Relative Length Change Research Articles

Study on two-phase displacement law considering mass transfer and diffusion

The influence of channeling on viscous fingering instability of CO2 miscible displacement is studied in the paper. Due to the viscous fingering not easily observed in porous media, channeling is used to simplify the viscous fingering instability. We adopted nonlinear simulation to investigate the development of viscous fingering instability during the displacement of Newtonian fluids in a channel by miscible fluids, and the influence of different Pe and different viscosity ratio R was studied. Under homogeneous conditions, when R is the same, the larger the Pe is, the more obvious the convection in the process of CO2 displacement is, the earlier the viscous fingering occurs, and the shorter the time for the finger to break through to the right boundary is. When Pe is the same, the larger the R is, the more unstable the contact area of miscible displacement becomes. More finger structures appear, and more complex fingering phenomena occur. The larger the R is, the earlier the fingering phenomenon appears, and the earlier it breaks through to the right boundary. In addition, we studied the change in Relative Mixing Length (RML) during the diffusion process quantitatively. Finally, our investigation delved into the impact of heterogeneity on viscous fingering. We observed that under significant heterogeneity, viscous fingering tends to manifest preferentially in the direction of increasing permeability.

Greater physiological resistance to heat may favour an invasive freshwater turtle, enabling it to outcompete native species in a changing climate

Abstract Climate warming and biological invasion can interact to affect ecosystems, and the results of such interactions depend on whether invaders show physiological advantages in their responses to warming environments as compared with native species after the establishment and local adaptation. However, it has rarely been evaluated. The present study compared the heat tolerance of a globally invasive turtle, the red‐eared slider Trachemys scripta elegans, and two co‐occurring native turtle species in China, the Chinese soft‐shelled turtle Pelodiscus sinensis and Chinese pond turtle Mauremys reevesii, after acclimation in the same thermal environment. The expression patterns of heat shock factor 1 (HSF1), multiple heat shock proteins (HSPs) and telomere reverse transcriptase (TERT), and changes in relative telomere length (RTL) were then evaluated in liver and muscle of turtles under thermal stress. The results showed that T. scripta elegans had greater physiological resistance to heat than the co‐occurring native turtle species, and that this higher tolerance was accompanied by a higher temperature induction of the peak expression of inducible HSPs in liver and a higher onset temperature for the main inducible HSPs in muscle. During thermal stress, T. scripta elegans showed a better ability to maintain the expression levels of TERT under extremely hot conditions, whereas high temperatures inhibited TERT in muscles of native turtle species. Meanwhile, thermal stress did not cause telomere erosion in any of the three turtle species and some treatments can lead to slightly longer telomeres in T. scripta elegans or M. reevesii. Overall, the invasive turtle species showed higher heat tolerance and physiological advantages in enduring hot weather in comparison to the co‐occurring native turtle species. This may favour these invaders in situations of climate warming. Our study highlights the role of physiological adaptations displayed by invaders in achieving advantages over native species under climate change.

Precipitation processes of Al-1.7 at% Cu and the influence of Au micro-alloying studied by dilatometry

Micro-alloying represents an important pathway in the design of modern Al-based alloys. It affects the precipitation kinetics during heat treatment which is crucial for optimization of the microstructure. In this study, difference dilatometry is applied to study precipitation processes in Al-1.7 at% Cu alloys with varying Au-content. A quantitative analysis is given for the base Al-Cu alloy on the formation of the metastable θ′-precipitate phase (Al2Cu) and its subsequent dissolution and transformation to the stable θ-precipitate phase (Al2Cu) upon time-linear heating starting from the state of supersaturated solid solution. The dilatometric analysis is enabled by the subtle balance of the relative length changes that arises, on the one hand, from the specific volume increase of the supersaturated Al matrix upon precipitation of the excess alloy component (Cu) and, on the other hand, from the specific volume variation associated with the formation of the precipitates. The relation between the observed relative changes and the amount of precipitates is supported by complementary simulation studies of the precipitation processes using MatCalc software. Micro-alloying with Au is found to promote the θ′-formation by an increasing nucleation and growth rate. In addition to the quantitative length change analysis, information on the kinetics of the θ′-formation is deduced from Kissinger analysis of the maximum rates of length change with temperature for different heating rates.

Mechanical, environmental, and economic assessment of sustainable cement mortar using Afghan natural pozzolan as a partial replacement for cement

Using natural pozzolan to produce cement-based mortar is one of the suitable solutions to reduce cost, energy consumption, and environmental impacts. In this experimental study, the paste replacement methodology (replacement of partial cement wt% with supplementary cementitious material) is used. Natural pozzolan, as vernacular material with high silicate aluminate originating in Afghanistan, is replaced (6, 13, and 20%) with cement in mortar. Various tests such as slump, compressive strength, tensile strength, water absorption, freezing-thawing cycles, relative length change, pull-off test, and microstructure analysis have been performed to study the properties of fresh and hardened mortar. The findings showed that the use of natural pozzolan containing a high level of silicate and aluminate as a replacement of cement in mortar improved 56 days compressive and tensile strength of mortar by 2.2 and 6%, respectively, water absorption was reduced by 1.6%, and the resistance to the freezing and thawing cycles was increased 10.7% as well compared to the reference samples. In addition, the results of economic analysis and sustainable development indicators assessment of mortar showed that using this replacement methodology was economically acceptable and reduced the potential of global warming and energy consumption by 13% of the production of one ton of cement using standard technology. The optimum replacement percentage was selected at 13% without compromising the mechanical properties of mortar.

Temperature-independent telomere lengthening with age in the long-lived human fish (Proteus anguinus).

Despite a number of studies showing a negative relationship between age and telomere length, the universality of this pattern has been recently challenged, mainly in ectothermic animals exhibiting diverse effects of age on telomere shortening. However, data on ectotherms may be strongly affected by the thermal history of the individuals. We thus investigated the age-related changes in relative telomere length in the skin of a small but long-lived amphibian living naturally in a stable thermal environment over its entire life, allowing comparison with other homeothermic animals like birds and mammals. The present data showed a positive relation between telomere length and individual age, independent of sex and body size. A segmented analysis highlighted a breakpoint in the telomere length-age relationship, suggesting that telomere length reached a plateau at the age of 25 years. Further studies focusing on the biology of animals that live much longer than expected based on body mass will contribute to our better understanding of how ageing processes evolved and may also bring innovation for extending human health span.

Changes in Relative Telomere Length in Patients with Obstructive Sleep Apnea Syndrome on the Background of CPAP Therapy: A Pilot Study

Changes in Relative Telomere Length in Patients with Obstructive Sleep Apnea Syndrome on the Background of CPAP Therapy: A Pilot Study

Advanced technique for measuring relative length changes under control of temperature and helium-gas pressure

We report the realization of an advanced technique for measuring relative length changes ΔL/L of mm-sized samples under the control of temperature (T) and helium-gas pressure (P). The system, which is an extension of the apparatus described in the work of Manna etal. [Rev. Sci. Instrum. 83, 085111 (2012)], consists of two 4He-bath cryostats, each of which houses a pressure cell and a capacitive dilatometer. The interconnection of the pressure cells, the temperature of which can be controlled individually, opens up various modes of operation to perform measurements of ΔL/L under the variation of temperature and pressure. Special features of this apparatus include the possibility (1) to increase the pressure to values far in excess of the external pressure reservoir, (2) to substantially improve the pressure stability during temperature sweeps, (3) to enable continuous pressure sweeps with both decreasing and increasing pressure, and (4) to simultaneously measure the dielectric constant of the pressure-transmitting medium, viz., helium, εr He(T,P), along the same T-P trajectory as that used for taking the ΔL(T, P)/L data. The performance of the setup is demonstrated by measurements of relative length changes (ΔL/L)T at T = 180 K of single crystalline NaCl upon continuously varying the pressure in the range 6 ≤ P ≤ 40 MPa.

Effect of Si and Al on Retained Austenite Stabilization during Q&P and Galvannealing Process

The present contribution concentrates on the different effects of Si and Al on the carbide precipitation and austenite decomposition during the Q&P-process and an additional galvannealing treatment of up to 560 °C. These effects have been investigated by dilatometry (derivation of relative length change) and differential scanning calorimetry (heat flow) during tempering. It was possible to show the beneficial effect of Si on retarding the carbide precipitation in tempered martensite and thereby the ability to stabilize higher amounts of retained austenite compared to Al. Furthermore, the effect on retained austenite decomposition during Q&P and subsequent galvannealing could be demonstrated. Here, Al has the benefit to increase the thermal stability of austenite during galvannealing.

Stretchable Transparent Polyelectrolyte Elastomers for All‐Solid Tunable Lenses of Excellent Stability Based on Electro–Mechano–Optical Coupling

AbstractLenses are ubiquitously used for imaging. Compared with conventional lenses containing rigid translating components driven by mechanical motors, nonmechanical tunable lenses have been drawing attention owing to their advantages in compactness, lightweight, low power consumption, and fast response. Herein, inspired by the accommodation mechanism of the human eye, an all‐solid electromechanically tunable lens driven by a dielectric elastomer actuator is presented. A soft, stretchable, transparent, and ionically conductive polyelectrolyte elastomer, poly(3‐acrylamidopropyl)trimethylammonium chloride, is synthesized and used as the electrodes, one of which is plano‐convex and the other planar. A mold‐free procedure is elaborated to eliminate the contamination by molding and for facile fabrication. Subject to voltage, the resulting tunable lens achieves a relative change of focal length of ≈46.4%, superior to that of the human eye. The electro–mechano–optical coupling of the lens is modeled and the theoretical predictions agree well with the experimental results. Moreover, the tunable lens responds fast, operates stably in the ambient and desiccated environment, maintains performances over 1000 cycles, and exhibits a shelf‐life longer than 12 weeks. The polyelectrolyte elastomer‐based all‐solid tunable lens promises a potential solution for lightweight, compact, and durable imaging systems.

Three months-longitudinal changes in relative telomere length, blood chemistries, and self-report questionnaires in meditation practitioners compared to novice individuals during midlife.

Aging accelerates during midlife. Researches have shown the health benefits of mind-body intervention (MBI). However, whether MBI is involved with aging process has not been well understood. In this study, we approach to examine the relations of MBI with this process by investigating an aging marker of the peripheral blood, blood chemistry, and self-report questionnaires. A quasi-experimental design was applied. Experienced MBI practitioners participated in a 3-month intensive meditation training, while the age, gender-matched MBI-naïve controls led a normal daily life. Measurements were taken at before and after the 3 months for relative telomere length (RTL), blood chemistry, and self-report questionnaires including items about sleep quality, somatic symptoms, depression, anxiety, stress, emotional intelligence (EI), and self-regulation. For RTL, the repeated measures analysis of variance showed a significant group*time interaction (P = .013) with a significant post hoc result (P = .030) within the control group: RTL was significantly reduced in the control while it was maintained in the meditation group. In repeated measures analysis of variance for blood chemistries, there were significant group differences between the groups in glucose and total protein. In the post hoc comparison analysis, at post measurements, the meditation group exhibited significantly lower values than the control group in both glucose and total protein. There were significant group-wise differences in the correlations of RTL with triglyceride (TG), high-density lipoprotein (HDL), glutamic oxaloacetic transaminase and glutamic pyruvic transaminase. Any of self-report results did not show significant changes in group*time interaction. However, there were group differences with significant (P < .05) or a tendency (.05 < P < .1) level. There were significant improvements in depression, stress and EI as well as tendencies of improvement in sleep quality and anxiety, in the meditation group compared to the control group. Our results suggest that meditation practice may have a potential to modify aging process in molecular cellular level combined with changes in psychological dimension.

Telomerase activity, relative telomere length, and longevity in alfalfa (Medicago sativa L.)

Background Medicago sativa L. ‘Qingshui’ is a valuable rhizomatous forage germplasm resource. We previously crossed Qingshui with the high-yielding Medicago sativa L. ‘WL168’ and obtained novel rhizomatous hybrid strains (RSA-01, RSA-02, and RSA-03). Telomere dynamics are more accurate predictors of survival and mortality than chronological age. Based on telomere analyses, we aimed to identify alfalfa varieties with increased stamina and longevity for the establishment of artificial grazing grasslands. Methods In this study, we performed longitudinal analysis of telomerase activity and relative telomere length in five alfalfa varieties (Qingshui, WL168, RSA-01, RSA-02, and RSA-03) at the age of 1 year and 5 years to examine the relationship among telomerase activity, rate of change in relative telomere length, and longevity. We further aimed to evaluate the longevity of the examined varieties. Telomerase activity and relative telomere length were measured using enzyme-linked immunosorbent assay and real-time polymerase chain reaction, respectively. Results We observed significant differences in telomerase activity between plants aged 1 year and those aged 5 years in all varieties except WL168, and the rate of change in telomerase activity does not differ reliably with age. As telomerase activity and relative telomere length are complex phenomena, further studies examining the molecular mechanisms of telomere-related proteins are needed. Relative telomere lengths of Qingshui, WL168, RSA-01, RSA-02, and RSA-03 in plants aged 5 years were higher than those aged 1 year by 11.41, 11.24, 9.21, 10.23, and 11.41, respectively. Relative telomere length of alfalfa tended to increase with age. Accordingly, alfalfa varieties can be classified according to rate of change in relative telomere length as long-lived (Qingshui, WL168, and RSA-03), medium-lived (RSA-02) and short-lived (RSA-01). The differences in relative telomere length distances of Qingshui, WL168, RSA-01, RSA-02, and RSA-03 between plants aged 1 and 5 years were 10.40, 13.02, 12.22, 11.22, and 13.25, respectively. The largest difference in relative telomere length was found between Qingshui and RSA-02 at 2.20. Our findings demonstrated that relative telomere length in alfalfa is influenced by genetic variation and age, with age exerting a greater effect.

Biceps Femoris Fascicle Lengths Increase after Hamstring Injury Rehabilitation to a Greater Extent in the Injured Leg.

Document changes in fascicle length during rehabilitation from hamstring injury of the injured and uninjured legs and secondarily to describe any association between these changes and reinjury rate. Multicentre case series. Fifty-two prospectively included hamstring injured athletes had their biceps femoris long head fascicle lengths measured at the start and end of rehabilitation using two-dimensional ultrasound. Absolute and relative changes in fascicle length were compared for each leg using linear mixed models. Participants were followed for six months after being cleared to return to sport for any reinjury. Fascicle lengths and rehabilitation duration were compared for those who reinjured and those who did not. Injured leg fascicle length was shorter at the start of rehabilitation (9.1 cm compared to 9.8 cm, p < 0.01 ) but underwent greater absolute and relative lengthening during rehabilitation to 11.1 cm (18% increase) compared to 10.2 cm (8% increase, p < 0.01 ) for the uninjured leg. There were no significant differences in any fascicle length parameter for the 5 participants who reinjured in the 6 months following their return to sport compared to those that did not reinjure. While both injured and uninjured legs displayed increases in fascicle length during rehabilitation, the larger fascicle length increases in the injured leg suggest that either a different training stimulus was applied during rehabilitation to each leg or there was a different response to training and/or recovery from injury in the injured leg. Reinjury risk appears to be independent of fascicle length changes in this cohort, but the small number of reinjuries makes any conclusions speculative.

Effect of Human Platelet Lysate as Cultivation Nutrient Supplement on Human Natal Dental Pulp Stem Cell In Vitro Expansion.

Despite several scientific or ethical issues, fetal bovine serum (FBS) remains the standard nutrient supplement in the mesenchymal stem cell cultivation medium. Cell amplification plays an important role in human stem cell therapies. Increasing interest in this field has supported attempts to find suitable human alternatives to FBS for in vitro cell propagation. Human platelet lysate (hPL) has recently been determined as one of them. Our study aimed to evaluate the influence of 2% hPL in the growth medium for in vitro expansion of human natal dental pulp stem cells (hNDP-SCs). The effect was determined on proliferation rate, viability, phenotype profile, expression of several markers, relative telomere length change, and differentiation potential of four lineages of hNDP-SCs. As a control, hNDP-SCs were simultaneously cultivated in 2% FBS. hNDP-SCs cultivated in hPL showed a statistically significantly higher proliferation rate in initial passages. We did not observe a statistically significant effect on mesenchymal stem cell marker (CD29, CD44, CD73, CD90) or stromal-associated marker (CD13, CD166) expression. The cell viability, relative telomere length, or multipotency remained unaffected in hNDP-SCs cultivated in hPL-medium. In conclusion, hPL produced under controlled and standardized conditions is an efficient serum supplement for in vitro expansion of hNDP-SCs.

Cascading Effects of Conspecific Aggression on Oxidative Status and Telomere Length in Zebra Finches.

Living in social groups may exacerbate interindividual competition for territory, food, and mates, leading to stress and possible health consequences. Unfavorable social contexts have been shown to elevate glucocorticoid levels (often used as biomarkers of individual stress), but the downstream consequences of socially stressful environments are rarely explored. Our study experimentally tests the mechanistic links between social aggression, oxidative stress, and somatic maintenance in captive zebra finches (Taeniopygia guttata). Over 64 d, we measured the effects of aggression (received or emitted) on the individual oxidative status, body condition, and changes in relative telomere length (rTL) of birds living in high- and low-social-density conditions. Using path analyses, we found that birds living at high social density increased their aggressive behavior. Birds receiving the highest number of aggressions exhibited the strongest activation of antioxidant defenses and highest plasmatic levels of reactive oxygen metabolites. In turn, this prevented birds from maintaining or restoring telomere length between the beginning and the end of the experiment. Received aggression also had a direct negative effect on changes in rTL, unrelated to oxidative stress. In contrast, emitted aggression had no significant effect on individual oxidative stress or changes in rTL. Body condition did not appear to affect the physiological response to aggression or oxidative stress. At low density, we found trends that were similar to those at high density but nonsignificant. Our study sheds light on the causal chain linking the social environment and aggressive behavior to individual oxidative stress and telomere length. The long-term consequences of socially induced stress on fitness remain to be characterized.

Relative Telomere Length Change in Colorectal Carcinoma and Its Association with Tumor Characteristics, Gene Expression and Microsatellite Instability.

Simple SummaryTelomeres are specialized repeat DNA sequences at the ends of each chromosome. The primary function of telomeres is to prevent genomic instability. Telomeres shorten with every cell division. The role of relative telomere length (RTL) change in colorectal cancer (CRC) is not fully understood. We studied RTL in CRC tissue and adjacent normal tissue from the same patients (n = 165). We found significant shortening of RTL in cancer tissue, irrespective of age group, gender, tumor pathology, location and microsatellite instability (MSI) status. However, shortening was more pronounced in low-grade tumors and in the presence of MSI. Gene expression data suggested an association of telomere shortening with rapid cell division (upregulation of DNA replication and cyclin-dependent kinase genes), as well as downregulation of apoptosis genes. CRC tissue showed upregulation of some telomere maintenance genes.We compared tumor and adjacent normal tissue samples from 165 colorectal carcinoma (CRC) patients to study change in relative telomere length (RTL) and its association with different histological and molecular features. To measure RTL, we used a Luminex-based assay. We observed shorter RTL in the CRC tissue compared to paired normal tissue (RTL 0.722 ± SD 0.277 vs. 0.809 ± SD 0.242, p = 0.00012). This magnitude of RTL shortening (by ~0.08) in tumor tissue is equivalent to RTL shortening seen in human leukocytes over 10 years of aging measured by the same assay. RTL was shorter in cancer tissue, irrespective of age group, gender, tumor pathology, location and microsatellite instability (MSI) status. RTL shortening was more prominent in low-grade CRC and in the presence of microsatellite instability (MSI). In a subset of patients, we also examined differential gene expression of (a) telomere-related genes, (b) genes in selected cancer-related pathways and (c) genes at the genome-wide level in CRC tissues to determine the association between gene expression and RTL changes. RTL shortening in CRC was associated with (a) upregulation of DNA replication genes, cyclin dependent-kinase genes (anti-tumor suppressor) and (b) downregulation of “caspase executor”, reducing apoptosis.

Cellular DNA effects of radiation and cancer risk assessment in cells with mitochondrial defects

Mitochondria play a key role in mediating non-targeted effects (NTE) post-radiation exposure. Mitochondrial DNA (mtDNA), due to its less efficient repair as compared to nuclear DNA, is more severely affected by radiation exposure and mutations in essential mtDNA genes can further exacerbate oxidative stress. Our objective was to evaluate the impact of mitochondrial defects on radiation-induced DDR and genomic instability, biomarkers that can foreshadow cancer development. To better understand this relationship, we used commercially available lymphoblastoid cell lines containing characterized mitochondrial mutations and studied the kinetics of DNA damage and relative telomere length (RTL) changes over time post 0.5 Gy X-ray exposure. Our work suggests that cells containing different mitochondrial mutations exhibit unique DNA damage and telomere length effects following radiation exposure. For example, a cell line containing a mitochondrial mutation in the ND4 subunit of complex 1 showed decreased growth rate, higher levels of persistent DNA damage, and telomere instability as compared to wild type. In contrast, a cell line with a mutation in the ATPase 6 mitochondrial protein showed more subtle negative alterations. These findings suggest mitochondrial integrity may play an important role in cellular changes that promote cancer. In total results indicate mitochondrial mutations can influence DNA damage kinetics and genomic instability and have long-term consequences in the ability to regain homeostasis following radiation exposure. These results may help explain, at least in part, the rationale for the persistent genomic instability often observed following a low dose of radiation and how it may promote cancer.

Intra-Individual Variability of Human Dental Pulp Stem Cell Features Isolated from the Same Donor.

It is primarily important to define the standard features and factors that affect dental pulp stem cells (DPSCs) for their broader use in tissue engineering. This study aimed to verify whether DPSCs isolated from various teeth extracted from the same donor exhibit intra-individual variability and what the consequences are for their differentiation potential. The heterogeneity determination was based on studying the proliferative capacity, viability, expression of phenotypic markers, and relative length of telomere chromosomes. The study included 14 teeth (6 molars and 8 premolars) from six different individuals ages 12 to 16. We did not observe any significant intra-individual variability in DPSC size, proliferation rate, viability, or relative telomere length change within lineages isolated from different teeth but the same donor. The minor non-significant variances in phenotype were probably mainly because DPSC cell lines comprised heterogeneous groups of undifferentiated cells independent of the donor. The other variances were seen in DPSC lineages isolated from the same donor, but the teeth were in different stages of root development. We also did not observe any changes in the ability of cells to differentiate into mature cell lines—chondrocytes, osteocytes, and adipocytes. This study is the first to analyze the heterogeneity of DPSC dependent on a donor.

Novel Sources of Tolerance to Aluminium Toxicity in Wild Cicer (Cicer reticulatum and Cicer echinospermum) Collections.

In acid soils, the toxic form of aluminium, Al3+, significantly inhibits root growth and elongation, leading to less water and nutrient uptake. Previous research had shown differential Al toxicity tolerance among cultivated Cicer arietinum L. (chickpea); however, the potential for developing tolerant cultivars is limited by the narrow genetic diversity of cultivated chickpeas. Recent collections from Turkey of wild Cicer species, Cicer reticulatum, and Cicer echinospermum, have increased the available gene pool significantly, but there has been no large-scale screening of wild Cicer for acid tolerance or Al3+ toxicity tolerance. This study evaluated 167 wild Cicer and 17 Australian chickpea cultivars in a series of screenings under controlled growth conditions. The pH of 4.2 and Al concentrations of 15 and 60 μM Al were selected for large-scale screening based on dose response experiments in a low ionic strength nutrient solution. The change in root length showed better discrimination between tolerant and sensitive lines when compared with shoot and root dry weights and was used as a selection criterion. In a large-scale screening, 13 wild Cicer reticulatum accessions had a higher root tolerance index (≥50%), and eight had higher relative change in root length (≥40%) compared with PBA Monarch, which showed greater tolerance among the Australian domestic cultivars screened. In general, C. reticulatum species were found to be more tolerant than C. echinospermum, while genetic population groups Ret_5, Ret_6, and Ret_7 from Diyarbakir and Mardin Province were more tolerant than other groups. Among C. echinospermum, Ech_6 from the Siv-Diyar collection site of the Urfa Province showed better tolerance than other groups. In this first detailed screening of aluminium toxicity tolerance in the new wild Cicer collections, we identified accessions that were more tolerant than current domestic cultivars, providing promising germplasm for breeding programs to expand chickpea adaptation to acid soils.

Microscopic modeling of non-normal incidence vertical external cavity surface-emitting laser cavities

The optimization of a V-cavity geometry to obtain intense ultrafast pulses for a modelocked vertical external-cavity surface-emitting laser is studied using an expanded form of the transverse Maxwell semiconductor Bloch equations. The influence of the incidence angle and relative cavity arm lengths is considered with respect to both the pump-probe computed instantaneous gain and group delay dispersion and the converged modelocked state. Changes in the angle are seen to lead to modest changes in dispersion but significant deformations of the modelocked pulse. Large changes in relative arm lengths are seen to lead to modest changes in the modelocked pulse with optimal pulses being observed with a 1:1 arm length ratio. The underlying microscopic dynamics are shown to drive these behaviors. This work provides a theoretical means to optimize experimental cavity geometry for desirable modelocking behaviors.

Features of Structural Formation in a Cu–Al Powder System

Investigations of the process of liquid-phase sintering of powder compositions of the Cu–Al system were carried out. As a result, the dependence of their final porosity indicators on the corresponding initial factors, comprising sintering temperatures and the number of constituent components, was revealed. Based on the obtained experimental data, the dependences of the microstructure of Cu–Al system compositions having a 25% aluminum content on sintering temperature and aluminum concentration are presented. In the course of the research, the dependence of the aluminum solid phase distribution in the Cu–Al system on the sintering temperature was studied at various concentrations. Experimental data on determining the porosity of the Cu–Al system compacts, the amount of the solid phase component in the liquid, as well as the amount of aluminum in the solid phase after sintering, depending on its initial concentration, are presented. The sintering of Cu–Al system compacts is shown to proceed with the participation of the liquid phase. In this case, changes in the dimensions of the sintered briquettes, on which the stability of the resulting powder blanks depends, turns out to be important. The technique and results of dilatometric studies of changes in compact dimensions depending on the sintering temperature and the initial porosity of the workpieces are presented. Additionally, the dependence of the relative change in the sample length and the medium temperature on the aluminum composition concentration was investigated.