Unveiling the brain’s symphony:exploring the necessity and sufficiency of neural networks in behavior control

Since the pioneering work by Broca and Wernicke in the 19th century,who examined individuals with brain lesions to associate them with specific behaviors,it was evident that behaviors are complex and cannot be fully attributable to specific brain areas alone.Instead,they involve connectivity among brain areas,whether close or distant.At that time,this approach was considered the optimal way to dissect brain circuitry and function.These pioneering efforts opened the field to explore the necessity or sufficiency of brain areas in controlling behavior and hence dissecting brain function.However,the connectivity of the brain and the mechanisms through which various brain regions regulate specific behaviors,either individually or collaboratively,remain largely elusive.Utilizing animal models,researchers have endeavored to unravel the necessity or sufficiency of specific brain areas in influencing behavior;however,no clear associations have been firmly established.

Machine Learning Techniques in Predicting Hot Deformation Behavior of Metallic Materials

In engineering practice,it is often necessary to determine functional relationships between dependent and independent variables.These relationships can be highly nonlinear,and classical regression approaches cannot always provide sufficiently reliable solutions.Nevertheless,Machine Learning(ML)techniques,which offer advanced regression tools to address complicated engineering issues,have been developed and widely explored.This study investigates the selected ML techniques to evaluate their suitability for application in the hot deformation behavior of metallic materials.The ML-based regression methods of Artificial Neural Networks(ANNs),Support Vector Machine(SVM),Decision Tree Regression(DTR),and Gaussian Process Regression(GPR)are applied to mathematically describe hot flow stress curve datasets acquired experimentally for a medium-carbon steel.Although the GPR method has not been used for such a regression task before,the results showed that its performance is the most favorable and practically unrivaled;neither the ANN method nor the other studied ML techniques provide such precise results of the solved regression analysis.

Increased excitatory amino acid transporter 2 levels in basolateral amygdala astrocytes mediate chronic stress–induced anxiety-like behavior

The conventional perception of astrocytes as mere supportive cells within the brain has recently been called into question by empirical evidence, which has revealed their active involvement in regulating brain function and encoding behaviors associated with emotions.Specifically, astrocytes in the basolateral amygdala have been found to play a role in the modulation of anxiety-like behaviors triggered by chronic stress. Nevertheless, the precise molecular mechanisms by which basolateral amygdala astrocytes regulate chronic stress–induced anxiety-like behaviors remain to be fully elucidated. In this study, we found that in a mouse model of anxiety triggered by unpredictable chronic mild stress, the expression of excitatory amino acid transporter 2 was upregulated in the basolateral amygdala. Interestingly, our findings indicate that the targeted knockdown of excitatory amino acid transporter 2 specifically within the basolateral amygdala astrocytes was able to rescue the anxiety-like behavior in mice subjected to stress. Furthermore, we found that the overexpression of excitatory amino acid transporter 2 in the basolateral amygdala, whether achieved through intracranial administration of excitatory amino acid transporter 2agonists or through injection of excitatory amino acid transporter 2-overexpressing viruses with GfaABC1D promoters, evoked anxiety-like behavior in mice. Our single-nucleus RNA sequencing analysis further confirmed that chronic stress induced an upregulation of excitatory amino acid transporter 2 specifically in astrocytes in the basolateral amygdala. Moreover, through in vivo calcium signal recordings, we found that the frequency of calcium activity in the basolateral amygdala of mice subjected to chronic stress was higher compared with normal mice.After knocking down the expression of excitatory amino acid transporter 2 in the basolateral amygdala, the frequency of calcium activity was not significantly increased, and anxiety-like behavior was obviously mitigated. Additionally, administration of an excitatory amino acid transporter 2 inhibitor in the basolateral amygdala yielded a notable reduction in anxiety level among mice subjected to stress. These results suggest that basolateral amygdala astrocytic excitatory amino acid transporter 2 plays a role in in the regulation of unpredictable chronic mild stress-induced anxiety-like behavior by impacting the activity of local glutamatergic neurons, and targeting excitatory amino acid transporter 2 in the basolateral amygdala holds therapeutic promise for addressing anxiety disorders.

Relationship between parenting stress and behavioral and emotional problems in preschool children: A mediation effect analysis

BACKGROUND Emotional reactions,such as anxiety,irritability,and aggressive behavior,have attracted clinical attention as behavioral and emotional problems in preschool-age children.AIM To investigate the current status of family rearing,parental stress,and behavioral and emotional problems of preschool children and to analyze the mediating effect of the current status of family rearing on parental stress and behavioral/emo-tional problems.METHODS We use convenience sampling to select 258 preschool children in the physical examination center of our hospital from October 2021 to September 2023.The children and their parents were evaluated using a questionnaire survey.Pearson's correlation was used to analyze the correlation between child behavioral and emotional problems and parental stress and family rearing,and the structural equation model was constructed to test the mediating effect.RESULTS The score for behavioral/emotional problems of 258 preschool children was(27.54±3.63),the score for parental stress was(87.64±11.34),and the score for parental family rearing was(31.54±5.24).There was a positive correlation between the behavioral and emotional problems of the children and the“hostile/mandatory”parenting style;meanwhile,showed a negative correlation with the“support/participation”parenting style(all P<0.05).The intermediary effect value between the family upbringing of parents in parental stress and children's behavior problems was 29.89%.CONCLUSION Parental family upbringing has a mediating effect between parental stress and behavioral and emotional problems of children.Despite paying attention to the behavioral and emotional problems of preschool-age children,clinical medical staff should provide correct and reasonable parenting advice to their parents to promote the mental health of preschool-age children.

Reproductive strategies and seeds behavior of Betula platyphylla Suk. Population

By the methods of morphological anatomy and investigation in the sample fields, the main studies were carried out such as morphological anatomy of reproductive organs, birch population’s reproductive ages, reproductive allotment value and seed behavior. The relationship between birch population and their surroundings was studied. The results showed that birch’s flower organs and its seeds were suitable well for spreading by wind. The seeds by wind can fly far away in a short time. The quantity of seed spreading greatly varied with different communities. Birch’s reproduction age can be changed in different ecological surroundings. The reproductive allotment value of birch was obviously different at different reproductive stages. In the mesic habitat, birch can grow well. The lowest reproductive age of them was 12, average age 15. In most cases the age of branches to bearing fruits was more than 18. The order of reproductive allotment values was as follows: a flowering phase > flower bud phase > fruit phase.

Reproductive Behavior and Underwater Calls in the Emei Mustache Toad,Leptobrachium boringii

The Emei mustache toad, Leptobrachium boringii （Megophryidae）, is terrestrial but breeds in permanent streams. Primarily, it has a polygynous mating system and polyandry also occurs. The species vigorously defends submerged nest sites. We report on a reproductive study at Mt. Emei, western China conducted in 2004, 2006, 2007, 2009, and 2011 during the breeding season. Males produce both advertisement and courtship calls underwater, and the latter differs from the former in having an additional trill-like last note of low intensity. Females might determine the oviposition location and hence the egg mass location. A low, submissive posture can be adopted by the male to avoid being attacked by other males. When fighting, the maxillary nuptial spines are employed as weapons, and males hold their opponents on their spines with the forelimbs that enlarge during the breeding season. Male body size and the quantity of fight wounds on its ventral side are positively correlated. Satellite male mating might exist in L. boringii. Additionally, underwater calls from another population of this species and a population of L. leishanense generally are similar to those of the population from Mt. Emei.

Impacts of grazing and mowing on reproductive behaviors of Stipa grandis and Stipa krylovii in a semi-arid area

Disturbance can affect biomass allocation of plants,but can it influence plant reproductive behavior?To address this issue,we performed field plant community investigations and explored the reproductive behaviors of Stipa grandis and Stipa krylovii in response to grazing and mowing treatments at Maodeng pasture of Xilinguole League of Inner Mongolia,China during 2007–2009.The results showed that,with a similar niche width for the two plant species under mowing and grazing treatments,mowing significantly increased the ratio of ramet to genet number of S.krylovii and the carbon to nitrogen ratio of S.grandis,and grazing significantly decreased the ratio of vegetative to reproductive tiller biomass of S.grandis and increased the ratio of vegetative to reproductive tiller number of S.krylovii.Regression analysis showed that the significantly positive effect of root to shoot biomass ratio was stronger on the ratio of vegetative to reproductive tiller number of S.grandis than on that of S.krylovii.These results indicated that grazing and mowing influenced the reproductive manner and the process of sexual reproduction of S.grandis and S.krylovii.

Relationship Between Behavioral Frequency and Reproductive Potential of Female Alpine Musk Deer in Captivity

Between June 2005 and February 2006, focal sampling and all occurrence behavior recording were used to quantify the behavioral patterns of captive female alpine musk deer （Moschus sifanicus） at Xinglongshan Musk Deer Farm, Gansu Province, China. Copulation success was used to differentiate individuals into two groups （successful and unsuccessful） and to provide a basis for behavioral comparisons, throughout both mating （rut） and non mating seasons. The results indicated significant differences between the behavior patterns of successful and unsuccessful females; however, the reproductive season played an important environmental factor. Pooling results across reproductive seasons, successfully copulating females showed significantly higher frequencies of vigilance and lower frequency of feeding behavior as compared with unsuccessfully copulating females. In the non-mating season, unsuccessfully copulating females had higher frequency of self-directed behavior, environment sniffing, and were less aggressive than successful copulating females. Furthermore, females who were successful at copulating also demonstrated tail-pasting behavior; however, this only occurred during the rut season. The results of this study can improve management practices for musk deer farms through increasing mating success and reducing maintenance costs. Furthermore, variation in behavior may also be used as a predictor of copulation success and reproductive potential, whereby females can be grouped and separated according to their reproductive history and past reproduction success.

Maternal Separation Affects Mothers’ Affective and Reproductive Behaviors as Well as Second Offspring’s Emotionality

Daily separation of rat pups from their mothers while the preweaning period has an impact on behavior and stress response of pups. We hypothesized that maternal separation may create a depression-like state in mother rats from which we separate the rat pups and decrease their reproductive function and fertility. Also, we aimed to evaluate the transmission degree of depression and anxiety across generations. Females aged 3 months were divided in two groups of 10 rats each. After a first mating and a first parturition, we conducted maternal separation 3 h during 22 days for the experienced group while the control group mothers kept their pups. At 4 months of age, females underwent behavioral tests and a second mating. Second generation’s pups were also subjected to behavioral tests. Behavioral tests showed that mothers which experienced separation were more depressive and anxious than control ones, also they had a lower litter size. Rats pups of the second generation whose mothers experienced maternal separation also revealed behavior changes akin to depression and anxiety. Thus, maternal separation causes depressive and anxious-likestates on mother rats which experienced separation and has an impact on their litter size. Also, consequences of maternal separation seem to last throughout generations.

Reproductive behavior in horseshoe crabs:Does density matter?

While the four species of horseshoe crabs share many common reproductive traits with respect to their reproductive systems, they do differ with respect to their mating behavior （monogamy vs. polygynandry）. Past research has attributed these differences to a number of factors including： spawning densities, operational sex ratios （OSR＇s）, male condition （or age）, environmental and/or genetic factors, or a combination thereof. Mating behaviors in the three Asian horseshoe crab species （Tachy-pleus gigas, T. tridentatus, and Carcinoscorpius rotundicauda） with low spawning densities and 1：1 operational sex ratios are typically monogamous. In Limuluspolyphemus, mating behavior is more variable ranging fi＇om monogamy to polygynandry. Here we provide evidence, through a long term behavioral study, that variation in mating behavior is influenced by population density in L. polyphemus. Our study population on two beaches in Connecticut （Long Island Sound） have a spawning density 400 times less than that found in Delaware Bay （0.002 females/m2 vs. 0.8 females/m2） but similar operational sex ratios. Between 90%-95% of all spawning females in CT were paired with only one male, thus exhibiting monogamous behavior. In contrast, between 30 and 60% of spawning females in Delaware Bay have more than one mate and produce clutches of eggs with multiple paternities. Male condition played no role in mating behavior in CT populations. We also observed that on average 18% of the females on the spawning beaches are single. These results suggest that population density is an important condition that determines mating behavior. Also, low population density may lead to decreased mate finding ability and lost opportunities for spawning

Study on Relationship between Reproductive Tract Infections and Personal Hygiene Behaviors among Vulnerable Married Women in Shanghai

Objective:To understand the influence of personal hygiene behaviors on reproductive tract infections (RTIs) and to provide evidence for the intervention among married women at childbearing age Methods:A total of 1 631 married women in 60 residence neighborhoods from 4 streets and 2 stagnant enterprises were selected by multistage cluster random sampling and interviewed face-to-face through questionnaires, laboratory tests assay and gynecological examination. All data were analyzed by SAS 8.2. Results:The positive detection rates of five target pathogens, trichomonas vaginalis, candida albicans, G.vaginalis, chlamydia trachomatis and Neisseria gonorrhoeae, in the study were 3.04%, 5.04%, 1.52%, 6.68%, and 0.12%, respectively. Personal hygiene practices and sexual behaviors among married women in the study were good in general. The vast majority of women (98.77%) rinsed their vulvae every day and more than half of the women (53.03%) took bath every day. In terms of the prevalence of endogenous infection, there were statistical differences between women who had different frequencies of rinsing their vulvae and taking bath; and for the prevalence of sexually transmitted infection, there were significant differences between women whose husband had different frequency of washing their external genital organs before sexual intercourses each time. The mostly adopted contraceptive methods among women ranked by frequency were intra-uterine devices (IUD) (68.69%), male condom (16.69%) and safe period (6.20%), among which male condom could prevent sexually transmitted infections. Multiple logistic regression analyses indicated that the frequency of taking bath, the husband washing his external genital organ before sexual intercourse and the age of marriage were the influencing factors of RTIs, too. Conclusion:It is very urgent that health educational intervention of RTIs among married women be conducted and especially the knowledge on condom's double effects on contraception and prevention of RTIs be disseminated to urge women to practice hygiene behavior to achieve the aim of preventing RTIs.

Reproductive Behaviors and Pairing Modes of Odontotermes fomosanus(Shiraki)Alates

[ Objectives ] To study the reproductive behaviors and the effect of different pairing modes on the developmental status of incipient colonies＇of Odontote- rmes fomosanus （Shiraki）. [ Methods ] We observed the reproductive behaviors of male alates, female Mates and mated alates respectively. Male and female Mates had 9 pairing modes and founded 170 incipient colonies under laboratory conditions. The effect of pairing mode on incipient colonies＇ developmental status was ana- lyzed. [ Results ] Two peaking hours of mating activity within the daily circadian rhythm of Mate activity appeared from 09：00 to 10：00, and from 21：00 to 22：00, respectively. Courtship behavior before mating consisted of touching with antennae, connecting into a ring （head-to-end）, and licking. The reproductive behavior （ calling, pairing, tandem, mating and oviposition） of nestmate pairs was different to that of non-nestmate pairs. The pairing time of non-nestmate pairs was signifi- candy longer than that of alates paired with siblings （P 〈 0.05 ）. The non-swarming alates could mate with swarming or non-swarming Mates and lay fertile eggs which hatched successfully. However, the survival rate of colonies founded by non-swarming alates was very low. The death rate of incipient colonies was in the range of 0.61% -0. 99% after three months, while the death rate of the colonies founded by swarming alates was in the range of 0.22% -0.58%. Females that had been experimentally prevented from mating could lay eggs, but the eggs did not hatch. [ Conclusion] There are two distinct hourly peaks of mating activity within each 24 hour period. Incipient colonies founded by outbreeding have the highest probability of survival.

Relationship of Food Craving Behavior with Body Mass Index and Body Composition in Reproductive Age Females

Objective: To estimate the relationship of Food Craving (FC) behavior with females’ Body Mass Index (BMI), and body-composition. Design, setting and participants: A cross-sectional study of 302 reproductive-age women from middle-socioeconomic class was conducted at the Health & Occupational-Environmental Laboratory. Variable Measures: A FC behavior questionnaire (FCQ) was designed and validated in 151 female subjects. This questionnaire evaluated five dimensions: FC-leisure, FC-psychological reactance, FC-depression, FC-anxiety/stress, and FC-anger. Dependent variables were Body Mass Index (BMI, kg/m2) and the body fat mass. Interventions: A second group of 151 women completed the FCQ. Anthropometrical variables were recorded using the International Society for the Advancement of Kinanthropometry procedure. Analysis: A multiple regression-analysis using STAT- ISTICS version 7 was performed to determine the relationship of FC behavior with anthropometrical variables described. Results: We demonstrated that 98.7% of women had FC behavior. Women with higher BMI had higher scores of FC-depressions (p = 0.02) and FC-anger (p = 0.007). Food craving behavior (p < 0.0008), and food psychological-reactance (p = 0.006), were positive predictors of BMI;food psychological reactance was also a positive predictor of upper and lower-body fat mass (p = 0.005) and (p = 0.008), respectively. Conclusion and Implications: The food craving behavior is a common problem in the female population. Food psychological reactance, in addition to another affective alteration that present the population of women are predictor variables for the increase in BMI and in body-fat mass. It is important that health professionals are aware of the affective states of their patients.

Influence of heat treatment on microstructure,mechanical and corrosion behavior of WE43 alloy fabricated by laser-beam powder bed fusion

Magnesium(Mg)alloys are considered to be a new generation of revolutionary medical metals.Laser-beam powder bed fusion(PBF-LB)is suitable for fabricating metal implants withpersonalized and complicated structures.However,the as-built part usually exhibits undesirable microstructure and unsatisfactory performance.In this work,WE43 parts were firstly fabricated by PBF-LB and then subjected to heat treatment.Although a high densification rate of 99.91%was achieved using suitable processes,the as-built parts exhibited anisotropic and layeredmicrostructure with heterogeneously precipitated Nd-rich intermetallic.After heat treatment,fine and nano-scaled Mg24Y5particles were precipitated.Meanwhile,theα-Mg grainsunderwent recrystallization and turned coarsened slightly,which effectively weakened thetexture intensity and reduced the anisotropy.As a consequence,the yield strength and ultimate tensile strength were significantly improved to(250.2±3.5)MPa and(312±3.7)MPa,respectively,while the elongation was still maintained at a high level of 15.2%.Furthermore,the homogenized microstructure reduced the tendency of localized corrosion and favoredthe development of uniform passivation film.Thus,the degradation rate of WE43 parts was decreased by an order of magnitude.Besides,in-vitro cell experiments proved their favorable biocompatibility.

Association of preschool children behavior and emotional problems with the parenting behavior of both parents

BACKGROUND Parental behaviors are key in shaping children’s psychological and behavioral development,crucial for early identification and prevention of mental health issues,reducing psychological trauma in childhood.AIM To investigate the relationship between parenting behaviors and behavioral and emotional issues in preschool children.METHODS From October 2017 to May 2018,7 kindergartens in Ma’anshan City were selected to conduct a parent self-filled questionnaire-Health Development Survey of Preschool Children.Children’s Strength and Difficulties Questionnaire(Parent Version)was applied to measures the children’s behavioral and emotional performance.Parenting behavior was evaluated using the Parental Behavior Inventory.Binomial logistic regression model was used to analyze the association between the detection rate of preschool children’s behavior and emotional problems and their parenting behaviors.RESULTS High level of parental support/participation was negatively correlated with conduct problems,abnormal hyperactivity,abnormal total difficulty scores and abnormal prosocial behavior problems.High level of maternal support/participation was negatively correlated with abnormal emotional symptoms and abnormal peer interaction in children.High level of parental hostility/coercion was positively correlated with abnormal emotional symptoms,abnormal conduct problems,abnormal hyperactivity,abnormal peer interaction,and abnormal total difficulty scores in children(all P<0.05).Moreover,paternal parenting behaviors had similarly effects on behavior and emotional problems of preschool children compared with maternal parenting behaviors(all P>0.05),after calculating ratio of odds ratio values.CONCLUSION Our study found that parenting behaviors are associated with behavioral and emotional issues in preschool children.Overall,the more supportive or involved the parents are,the fewer behavioral and emotional problems the children experience;conversely,the more hostile or controlling the parents are,the more behavioral and emotional problems the children face.Moreover,the impact of fathers’parenting behaviors on preschool children’s behavior and emotions is no less significant than that of mothers’parenting behaviors.

BCCLR:A Skeleton-Based Action Recognition with Graph Convolutional Network Combining Behavior Dependence and Context Clues

In recent years,skeleton-based action recognition has made great achievements in Computer Vision.A graph convolutional network(GCN)is effective for action recognition,modelling the human skeleton as a spatio-temporal graph.Most GCNs define the graph topology by physical relations of the human joints.However,this predefined graph ignores the spatial relationship between non-adjacent joint pairs in special actions and the behavior dependence between joint pairs,resulting in a low recognition rate for specific actions with implicit correlation between joint pairs.In addition,existing methods ignore the trend correlation between adjacent frames within an action and context clues,leading to erroneous action recognition with similar poses.Therefore,this study proposes a learnable GCN based on behavior dependence,which considers implicit joint correlation by constructing a dynamic learnable graph with extraction of specific behavior dependence of joint pairs.By using the weight relationship between the joint pairs,an adaptive model is constructed.It also designs a self-attention module to obtain their inter-frame topological relationship for exploring the context of actions.Combining the shared topology and the multi-head self-attention map,the module obtains the context-based clue topology to update the dynamic graph convolution,achieving accurate recognition of different actions with similar poses.Detailed experiments on public datasets demonstrate that the proposed method achieves better results and realizes higher quality representation of actions under various evaluation protocols compared to state-of-the-art methods.

Integrated ribosome and proteome analyses reveal insights into sevoflurane-induced long-term social behavior and cognitive dysfunctions through ADNP inhibition in neonatal mice

A growing number of studies have demonstrated that repeated exposure to sevoflurane during development results in persistent social abnormalities and cognitive impairment.Davunetide,an active fragment of the activity-dependent neuroprotective protein(ADNP),has been implicated in social and cognitive protection.However,the potential of davunetide to attenuate social deficits following sevoflurane exposure and the underlying developmental mechanisms remain poorly understood.In this study,ribosome and proteome profiles were analyzed to investigate the molecular basis of sevoflurane-induced social deficits in neonatal mice.The neuropathological basis was also explored using Golgi staining,morphological analysis,western blotting,electrophysiological analysis,and behavioral analysis.Results indicated that ADNP was significantly down-regulated following developmental exposure to sevoflurane.In adulthood,anterior cingulate cortex(ACC)neurons exposed to sevoflurane exhibited a decrease in dendrite number,total dendrite length,and spine density.Furthermore,the expression levels of Homer,PSD95,synaptophysin,and vglut2 were significantly reduced in the sevoflurane group.Patch-clamp recordings indicated reductions in both the frequency and amplitude of miniature excitatory postsynaptic currents(mEPSCs).Notably,davunetide significantly ameliorated the synaptic defects,social behavior deficits,and cognitive impairments induced by sevoflurane.Mechanistic analysis revealed that loss of ADNP led to dysregulation of Ca^(2+)activity via the Wnt/β-catenin signaling,resulting in decreased expression of synaptic proteins.Suppression of Wnt signaling was restored in the davunetide-treated group.Thus,ADNP was identified as a promising therapeutic target for the prevention and treatment of neurodevelopmental toxicity caused by general anesthetics.This study provides important insights into the mechanisms underlying social and cognitive disturbances caused by sevoflurane exposure in neonatal mice and elucidates the regulatory pathways involved.

Structural model of factors relating to the health promotion behavior of reproductive health among Indonesian adolescents

Objectives:We aim to explore the factors related to the health promotion behavior of reproductive health(RH)among Indonesian adolescents via structural equation modeling.Methods:A cross-sectional quantitative study was used to measure 108 adolescents aged 12-16 years.We employed a self-administered questionnaire developed from the health promotion model(HPM)and the empowerment model(EM)on the basis of self-efficacy to determine the factors related to health promotion in maintaining RH behavior.Structural equation modeling(SEM)was used to examine re-lationships among the variables.The Analysis of Moment Structures(AMOS)approach was used to evaluate if the proposed model is suitable for the data based on goodness-of-fit indices.Results:The model is appropriate for the data.Three interrelationships emerge among independent variables(P>0.05),namely,personal and cognitive behaviors(r=-0.01),cognitive and health pro-motion behaviors(r=0.09),and affective and health promotion behaviors(r=-0.17).The strongest relationship is between empowerment and health promotion behavior(r=0.72).Affection(interper-sonal and situational influences),immediate competing demands and preferences,and empowerment(participation and control)are directly related to RH behavior maintenance.Meanwhile,willingness of adolescents,prior related behavior,personal factor,and commitment to a plan of action are indirectly related to RH behavior maintenance.The model explains 43.9%of the variance in maintaining RH behavior.Conclusions:The HPM and EM models help determine the factors related to RH behavior maintenance among adolescents.Intervention to promote RH among Indonesian adolescents should begin from the level of child-parent-health care professional encounter for empowering the RH of adolescents.

Thermally-induced cracking behaviors of coal reservoirs subjected to cryogenic liquid nitrogen shock

The benefits of using cryogenic liquid nitrogen shock to enhance coal permeability have been confirmed from experimental perspectives.In this paper,we develop a fully coupled thermo-elastic model in combination with the strain-based isotropic damage theory to uncover the cooling-dominated cracking behaviors through three typical cases,i.e.coal reservoirs containing a wellbore,a primary fracture,and a natural fracture network,respectively.The progressive cracking processes,from thermal fracture initiation,propagation or cessation,deflection,bifurcation to multi-fracture interactions,can be well captured by the numerical model.It is observed that two hierarchical levels of thermal fractures are formed,in which the number of shorter thermal fractures consistently exceeds that of the longer ones.The effects of coal properties related to thermal stress levels and thermal diffusivity on the fracture morphology are quantified by the fracture fractal dimension and the statistical fracture number.The induced fracture morphology is most sensitive to changes in the elastic modulus and thermal expansion coefficient,both of which dominate the complexity of the fracture networks.Coal reservoir candidates with preferred thermal-mechanical properties are also recommended for improving the stimulation effect.Further findings are that there exists a critical injection temperature and a critical in-situ stress difference,above which no thermal fractures would be formed.Preexisting natural fractures with higher density and preferred orientations are also essential for the formation of complex fracture networks.The obtained results can provide some theoretical support for cryogenic fracturing design in coal reservoirs.

Shear behavior of single-joint bolted sandstone subjected to dryewet cycles:Experimental and analytical approaches

A series of direct shear tests under constant normal loading conditions were carried out on specimens of bolted sandstone single-joint treated with different numbers of dryewet cycles.The experimental results show that the peak shear strength and shear stiffness of bolted sandstone joints were significantly reduced after 12 dryewet cycles.The decrease in the shear strength of rough joints is more significant than that of flat joints.Due to the decrease in the strength of the surrounding rock,the deformation characteristics of the bolts are significantly affected by the number of dryewet cycles performed.With an increase in the number of dryewet cycles,the plastic hinge length of the bolt gradually increases,resulting in an increase in the corresponding shear displacement when the bolt breaks.Compared with the tensileeshear failure mode of the bolts in flat joints,the tensileebending failure mode arises for bolts in rough joints.A shear curve model describing the whole process of bolted rock joints is established based on the deterioration of rock mechanical parameters caused by dry‒wet cycles.The model proposed considers the change in the friction angle of the joint surface with the shear displacement,which is applied to the derivation of the model by introducing the dynamic evolutionary friction angle parameter.The reasonably good agreement between a predicted curve and the corresponding experimental curve indicates that this method can effectively predict the shear strength of a bolted rock joint involving rough joint under dryewet cycling conditions.