Duration Of Contact Research Articles

Erosion of CAD/CAM restorative materials and human enamel: An in vitro study

This in vitro study used the same frequency and duration of acid contact as a previous in situ/in vivo study to evaluate the effect of erosion on CAD/CAM restorative materials and human enamel and to compare the effects of in vitro and in situ/in vivo acid challenges on CAD/CAM restorative materials and human enamel. The CAD/CAM restorative materials (IPS e.max CAD, Lava Ultimate, and PMMA block) and human enamel were eroded by immersion in 150 ml of cola drink for 14 days (4 × 5 min/day). The surface microhardness and surface roughness of the specimens were measured at baseline (T1), day 7 (T2), and day 14 (T3). The substance losses were measured at T2 and T3. The data were statistically analyzed using repeated measures ANOVA and Bonferroni's test (α = 0.05). Erosion significantly decreased the surface microhardness of the CAD/CAM restorative materials and human enamel (all P < 0.001). The overall percentage of surface microhardness loss (%SMHl) of the PMMA block and enamel due to in vitro erosion was significantly higher than that due to in situ/in vivo erosion (P = 0.02 and P < 0.001, respectively). Consistent with in situ/in vivo erosion, the surface roughness and profile of the tested restorative materials remained unchanged after in vitro erosion. A significant increase in the surface roughness and substance loss was observed for enamel after in vitro erosion (all P < 0.001). The overall substance loss of enamel due to in vitro erosion was significantly higher than that due to in situ/in vivo erosion (P < 0.001). In conclusion, erosion decreased the surface microhardness of the CAD/CAM restorative materials and human enamel. Moreover, erosion negatively influenced the substance loss and surface roughness of human enamel. For the substance loss of enamel and %SMHl of PMMA block and enamel, the in vitro erosive effects were approximately 1–2 times greater than the in situ/in vivo effects. However, for the surface roughness and profile of the CAD/CAM restorative materials, no significant difference was found between in vitro and in situ/in vivo erosion.

Macro-microscopic changes in the kidneys of the rats affected by methyl tertiary butyl ether in different time of the research

Methyl tert-butyl ether (MTBE) is a relatively new anthropogenic factor of environmental pollution. It is already known that it is an environmentally hazardous substance that has a toxic effect on the human body. The purpose of the research is to study the effect of MTBE on the structural organization of the kidneys of research animals. White outbred rats were involved into the research, which were treated with 500 mg/kg MTBE in an oil solution, which was administered intragastrically using a gastric catheter. Structural changes in the kidneys on the 3rd, 8th, 15th, 22nd and 60th day of the research were studied by means of light-optical and electron microscopy. The obtained material was processed statistically using the parametric Student's test and the nonparametric Kolmogorov-Smirnov test in accordance with the principles of variation statistics. During the runtime of the research, we have clearly defined the staging of changes in the structural organization of the kidney and the dependence of their severity on the duration of MTBE action. With short-term exposure (3, 8 and 15 day of the research), the weight of the kidneys and other organometric parameters do not differ from those in the control group. In the initial stages of MTBE action, we have observed reactive changes, which are clearly manifested in the structures of the filtration barrier (3rd day), and with an increase in the observation period (8th day) they spread to the epithelial cells of the proximal tubules. After 15 days of MTBE action, against the background of pronounced compensatory-adaptive events, we have noticed the development of dystrophic-destructive processes in the renal corpuscles and in the proximal tubules. There are structural signs of enhanced synthetic activity in the mesangial cells. On the 22nd day of the experiment, the morphometric index of the mass and linear dimensions of the kidneys increase in comparison with the control group. There are structural signs of atrophy and hypertrophy processes in the nephrons. There are progressive changes in the tubular apparatus of the kidneys in comparison with the previous period of the research. Long-term action of MTBE (60 days) causes further deepening of dystrophic and destructive changes in all parts of the nephron, which differ in intensity. It has been proved that MTBE has a negative effect on all structural components of the nephron, which leads to disorganization of the filtration and reabsorption of kidney apparatus and significant development of the connective tissue, which causes the development of sclerosis. Besides, it has been proved that MTBE has an apparent nephrotoxic effect and the degree of damage to the structural components of the kidney is determined by the duration of the body's contact with this toxic substance.

Odor discrimination in terrestrial and aquatic environments in California sea lions (Zalophus californianus) living in captivity

Pinnipeds, as any mammal species, use multimodal signals, including olfactory ones, to ensure vital functions. Thus, some pinniped species seem able to use olfaction in both social and foraging contexts and to discriminate between different odors in air including both natural and artificial odors, but studies on that topic remain scarce. Here, we studied the olfactory capabilities of California sea lions living in captivity at La Flèche Zoo (France) in both terrestrial and aquatic environments. We used two categories of odors: social odors (from familiar individuals of the same group, unfamiliar individuals from another Zoo, animal zookeepers and a terrestrial carnivore) and non-social odors (food and odors identified as repellents in certain vertebrates). Several behavioral parameters were measured and analyzed as the number and duration of contact with the odor, mouth openings, vocalizations (air only) and air bubble production (water only). Our results, although limited by the low number of animals monitored (n = 5), suggest that California sea lions are able to discriminate between different odors both in the air and under water. In the aquatic environment, the process allowing the perception of odors remains to be characterized. Applications to this work could be considered in captive conditions as well as in the wild.

Cytogenetic features of buccal epithelium under exposure to harmful factors of metallurgical production.

At the present stage of development of society, the issues of preserving and strengthening the most important productive force that determine the economic development and national security of the country remain relevant. Metallurgy is one of the basic industries in Russia, which forms up to 20% of GDP. This study assesses the condition of the oral mucosa in workers in the industry. To evaluate the formation of micronuclei in buccal cells as an early biomarker of health disorders as a result of occupational exposure to production factors of a metallurgical plant. Hygienic and clinical laboratory tests were carried out for workers of the metallurgical plant of the Republic of Bashkortostan. Cytological studies of the buccal epithelium were performed. Statistical processing of the results was carried out using the applied programs IBM, SPSS, Statistics, Microsoft Excel. The general assessment of working conditions in accordance with the criteria of R.2.2.2006-05 for workers of the metallurgical plant was established as 3.2-3.3. Analysis of the buccal epithelium revealed the occurrence of cells with cytogenetic disorders in the workers of the main group. Cells with atypical nuclei were identified in workers with a duration of contact with unfavorable factors of production for more than ten years. Signs of nuclear destruction were revealed, characterizing an increase in apoptotic activity in workers with prolonged contact times. Studies have shown that with more than 10 years of work experience, proliferation processes prevail over differentiation processes. The results obtained can be used as diagnostic methods that expand the prospects for identifying pre-pathological and pathological conditions.

Contact tracing of staff in the emergency department during the COVID-19 pandemic.

Contact tracing of staff in the emergency department during the COVID-19 pandemic.

Antimicrobial Efficacy of Silver Nanoparticles as Root Canal Irrigant's: A Systematic Review.

Removal of microbes is imperative during endodontic therapy. Due to their antimicrobial property, silver nanoparticles have been used for endodontic irrigation of the root canals. The objective of the present study was to provide a qualitative analysis of the published literature assessing silver nanoparticles as root canal irrigants. A search of PubMed, SCOPUS, Web of Science, and Embase databases was done without any time restriction. Articles published in English were included. Data were extracted and the risk of bias was assessed. Of the 154 studies identified, after screening according to the inclusion criteria, five in vitro studies were included. The results indicate that silver nanoparticles have an anti-microbial effect to varying degrees depending on certain factors. Within the limitations of the present studies that have a moderate to low risk of bias, an antimicrobial effect of silver nanoparticles is observed. Silver nanoparticles have the potential to be used as endodontic irrigants, although their efficacy depends on particle size and the duration of contact which require further investigation.

Graph modelling for tracking the COVID-19 pandemic spread

The modelling is widely used in determining the best strategies for the mitigation of the impact of infectious diseases. Currently, the modelling of a complex system such as the spread of COVID-19 infection is among the topical issues. The aim of this article is graph-based modelling of the COVID-19 infection spread. The article investigates the studies related to the modelling of COVID-19 pandemic and analyses the factors affecting the spread of the disease and its main characteristics. We propose a conceptual model of COVID-19 epidemic by considering the social distance, the duration of contact with an infected person and their location-based demographic characteristics. Based on the hypothetical scenario of the spread of the virus, a graph model of the process are developed starting from the first confirmed infection case to human-to-human transmission of the virus and visualized by considering the epidemiological characteristics of COVID-19. The application of graph for the pandemic modelling allows for considering multiple factors affecting the epidemiological process and conducting numerical experiments. The advantage of this approach is justified with the fact that it enables the reverse analysis the spread as a result of the dynamic record of detected cases of the infection in the model. This approach allows for to determining undetected cases of infection based on the social distance and duration of contact and eliminating the uncertainty significantly. Note that social, economic, demographic factors, the population density, mental values and etc. affect the increase in number of cases of infection and hence, the research was not able to consider all factors. In future research will analyze multiple factors impacting the number of infections and their use in the models will be considered.

Monkey see, monkey tap: mimicry of movement dynamics during coordinated tapping.

Common social behaviors, such as having a conversation, dancing, or playing a team sport, require precise interpersonal coordination of action. One question that emerges in research on interpersonal coordination is to what extent individuals implicitly mimic the spatial characteristics of movements for tasks that emphasize movement timing. To investigate this question, we conducted two experiments using an interpersonal synchronization-continuation tapping paradigm in which pairs of individuals tapped with their index finger on a table in synchrony with an auditory metronome and then continued tapping at the same tempo when the metronome stopped. Pairs of individuals tapped either together with the instruction to maintain synchrony with each other (interpersonal tapping) or tapped alone (solo tapping). Solo tapping conditions either occurred with their tapping partner present in the testing room (Experiment 1) or absent (Experiment 2). We used motion capture to examine both the spatial and temporal aspects of movement dynamics during task performance. In both experiments, participants implicitly mimicked subtle aspects of spatial elements of their partner's movements. The extent of finger extension (tap amplitude) and, in Experiment 1, duration of finger contact with the surface (dwell time) were correlated between tapping partners when they tapped together. In some cases, this spatial mimicry extended to solo tapping conditions, but only during solo tapping conditions that followed the interpersonal tapping task, and, to a lesser degree, when solo tapping after having observed the other participant solo tapping.

Vital Tooth Whitening Techniques. A Literature Review

Background: Vital tooth whitening has become an integral part of esthetic dentistry and remains one of the safest and most economical options today to improve dental esthetics without removing tooth structure. The tooth whitening materials have evolved into three categories: dentist- prescribed/dispensed in office, the dentist prescribed patient home use, and over-the-counter purchased and applied by patients. Objective: This review outlines the latest advances in dentist prescribed vital teeth whitening techniques, effects on tooth structure, soft tissues, and dental restoratives. Areas requiring additional research are also discussed. Methods: Electronic and manual literature search was conducted for key words such as tooth bleaching, and dental bleaching techniques using PubMed/MEDLINE, followed by manual selection of the studies that included whitening procedures in vital teeth. Results: The two main whitening agents are carbamide peroxide (CP) and hydrogen peroxide (HP or H2O2) whose concentration, duration of contact and total treatment time can alter results. In addition, factors including the type of stain and the age of the patient can affect results. Although whitening agents can affect tooth structure, restorative materials, and gingival tissues, the changes are temporary or can be treated using minimally invasive techniques. Conclusion: Areas requiring further research include the actual mechanism of whitening, its effect on tooth structure and restorative materials, and the development of an easy method to quantitate the degree of whitening in the dental office.

Chronic herpetic stomatitis: prevention aimed at reducing the number of active sources of infection

One of the most common conditions in dental practice is herpetic stomatitis, caused by the herpes simplex virus type 1. The aim of the study was to evaluate the therapeutic and preventive effect of complex therapy of chronic herpetic stomatitis caused by the herpes simplex virus type 1. The study included 100 patients with chronic herpetic stomatitis aged 26 to 70 years, 50 of whom received standard treatment, and 50 received additional drugs «Timalin», «Leikinferon», «Stomat» and blue light radiation directly on the area of the formations. The results showed a significant reduction in the duration of the active stage of the disease, an increase in the duration of remission and a reduction in the number of relapses. The proposed therapeutic complex is an important link in the prevention of herpesvirus infection, which significantly reduces both the number of people with active infection and the duration of contact of dental clinic staff with patients who have the virus detected in saliva.

Graph modelling for tracking the COVID-19 pandemic spread

The modelling is widely used in determining the best strategies for the mitigation of the impact of infectious diseases. Currently, the modelling of a complex system such as the spread of COVID-19 infection is among the topical issues. The aim of this article is graph-based modelling of the COVID-19 infection spread. The article investigates the studies related to the modelling of COVID-19 pandemic and analyses the factors affecting the spread of the disease and its main characteristics. We propose a conceptual model of COVID-19 epidemic by considering the social distance, the duration of contact with an infected person and their location-based demographic characteristics. Based on the hypothetical scenario of the spread of the virus, a graph model of the process are developed starting from the first confirmed infection case to human-to-human transmission of the virus and visualized by considering the epidemiological characteristics of COVID-19. The application of graph for the pandemic modelling allows for considering multiple factors affecting the epidemiological process and conducting numerical experiments. The advantage of this approach is justified with the fact that it enables the reverse analysis the spread as a result of the dynamic record of detected cases of the infection in the model. This approach allows for to determining undetected cases of infection based on the social distance and duration of contact and eliminating the uncertainty significantly. Note that social, economic, demographic factors, the population density, mental values and etc. affect the increase in number of cases of infection and hence, the research was not able to consider all factors. In future research will analyze multiple factors impacting the number of infections and their use in the models will be considered.

Penggunaan Limbah Kulit Singkong pada Filter Air Sederhana Skala Rumah Tangga

Cassava (Manihot utillisima) is a staple food for Indonesians after rice and corn. Cassava is a natural product (product) which is abundant in Indonesia, especially in the areas of Central Tawa and West Java. Activated carbon is a porous material derived from carbon material by combustion or thermal decomposition. Activated carbon is widely used for water purification, medicine, waste treatment and as a filter in compressed air (Lam et al., 2017). The purpose of this research is the quality of activated charcoal from cassava peel absorption capacity of activated carbon from cassava peels as a water filter, especially for removal of Cu (II) metal with a variety of activators and the optimum duration of contact with the use of activated carbon in a simple home scale water filter. The results showed that the quality of activated charcoal from coffee grounds which includes the quality of yield, moisture content, ash content and absorption of iodine has met SNI No.06-3730- 1995 Activated Charcoal Quality Standards. The higher the concentration, the greater the absorption of activated charcoal on Cu (II) metal, and from the variation data the most optimal activator is activated charcoal with a KOH activator of 0.3 m. The results of boxing the activated charcoal within 5 hours with an average yield of 0.1898 mg per liter meet the clean water standards, namely according to the 2008 East Java Regional Regulation which states that the Cu content in water is at a threshold of 0.2 mg per liter.

Identification of dominant risk factor involved in spread of COVID-19 using hesitant fuzzy MCDM methodology

The outburst of the pandemic Coronavirus disease since December 2019, has severely impacted the health and economy worldwide. The epidemic is spreading fast through various means, as the virus is very infectious. Medical science is exploring a vaccine, only symptomatic treatment is possible at the moment. To contain the virus, it is required to categorize the risk factors and rank those in terms of contagion. This study aims to evaluate risk factors involved in the spread of COVID-19 and to rank them. In this work, we applied the methodology namely, Fuzzy Analytic Hierarchy Process (FAHP) to find out the weights and finally Hesitant Fuzzy Sets (HFS) with Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is applied to identify the major risk factor. The results showed that “long duration of contact with the infected person” the most significant risk factor, followed by “spread through hospitals and clinic” and “verbal spread”. We showed the appliance of the Multi Criteria Decision Making (MCDM) tools in evaluation of the most significant risk factor. Moreover, we conducted sensitivity analysis.

ОЦЕНКА БЕЗОПАСНОСТИ ПРИМЕНЕНИЯ ПОЛИМЕРНОГО МАТЕРИАЛА «ПЕНОПЛЕКС» В ЖИВОТНОВОДСТВЕ

The article presents data on veterinary and sanitary and hygienic assessment of the polymer material «Penoplex». The above material is made of Styrofoam and used in many areas of production, including to reduce heat loss of livestock facilities. Cattle and pig manure was used as a contact medium with the material under study. The duration of contact with the material (exposure) was 30 days. To study the resistance of the material to disinfectants, we used: 10 % sodium hydroxide solution (80 °C); 5 % solution of soda ash (70 °C); clarified solution of bleach containing 3 % active chlorine; 40 % solution of formaldehyde; 2 % solution of hydrogen peroxide. Studies of samples of the polymer material «Penoplex» for resistance to animal secretions and disinfectants have shown that the polymer material is resistant to them. During the experiment and after its completion, the «Penoplex» material had no visually visible changes on the outer layer. The used disinfectants and the model environment did not violate the structure of the polymer material «Penoplex». A slight change in the color of the «Penoplex» was found on the 20th day of exposure to 10 % solution of sodium hydroxide with temperature of 70 °C. For sanitary and bacteriological evaluation of «Penoplex», the disk method was used. Discs with a diameter of 10 mm were prepared from the material under study; wood discs were used as a control. Studies have found that Penoplex has no effect on sanitary-indicative microorganisms and is neutral in relation to their growth, which indicates the absence of release of substances from it into the environment that can delay or stimulate the growth of test cultures. The veterinary and sanitary and hygienic assessment of the polymer material «Penoplex» is the basis to recommend it for use in the construction of livestock buildings and inclusion as an addition to the current «List of polymer materials and structures permitted for use in the construction and technological equipment of livestock facilities» in the prescribed manner.

A descriptive phenomenological model for white layer formation in hard turning of AISI 52100 bearing steel

This paper investigates the characteristics and the formation of white layers and dark layers induced by hard turning of through-hardened AISI 52,100 steel. The investigation showed that different types of white layers exist e.g., formed predominantly through excessive thermal or mechanical energy loading. The thermally induced white layer is formed when the cutting temperature is above the critical austenitisation temperature for the material. The nano-sized microstructure is initiated through dynamic recovery, which transitions to dynamic recrystallisation when the temperature rises above the onset temperature for dynamic recrystallisation. The corresponding white layer is characterised by a higher retained austenite content compared to the unaffected material, and the presence of a dark layer beneath the white layer. The white layer and the adjacent dark layer are found to be ∼12% harder and 14% softer, respectively, compared to the unaffected material. On the other hand, the mechanically induced white layer is formed through severe plastic deformation, where the formation is controlled by dynamic recovery and results in an elongated and broken-down substructure. Neither austenite nor an adjacent dark layer could be found for such white layers. The mechanically induced white layer is ∼26% harder than the unaffected material. For both types of white layer, (Fe, Cr)3C carbides are found in the microstructure. The investigation shows that the heating rate, cooling rate, pressure, and duration of contact between the cutting tool and workpiece surface should also be considered to understand the underlying formation mechanisms. The characteristics of the examined white layers and the cutting conditions are summarised in a descriptive phenomenological model in order to create a systematic approach for the definition of the different types of white layers.

Muscle Cryoinjury and Quantification of Regenerating Myofibers in Mice.

Cryoinjury, or injury due to freezing, is a method of creating reproducible, local injuries in skeletal muscle. This method allows studying the regenerative response following muscle injuries in vivo, thus enabling the evaluation of local and systemic factors that influence the processes of myofiber regeneration. Cryoinjuries are applicable to the study of various modalities of muscle injury, particularly non-traumatic and traumatic injuries, without a loss of substantial volume of muscle mass. Cryoinjury requires only simple instruments and has the advantage over other methods that the extent of the lesion can be easily adjusted and standardized according to the duration of contact with the freezing instrument. The regenerative response can be evaluated histologically by the average maturity of regenerating myofibers as indicated by the cross-sectional areas of myofibers with centrally located nuclei. Accordingly, cryoinjury is regarded as one of the most reliable and easily accessible methods for simulating muscle injuries in studies of muscle regeneration.

Nano-Structured Polyaniline as a Potential Adsorbent for Methylene Blue Dye Removal from Effluent

The textile sector is one of the major culprits of water pollution, and demands immediate attention. The coloured textile effluent, loaded with toxic dyes, when mixed with waterbodies, may harm aquatic life, plants, animals, and humans. Although polyaniline in its different forms was utilised for the adsorption of different dyes, the pure nano-fibrous form of polyaniline, i.e., PANI nanofibers, have reportedly not been used for the removal of dyes from wastewater. The present study aimed to employ nano-structured polyaniline, in the form of polyaniline nanofibers (base; PNB—polyaniline nanofiber base) for the elimination of methylene blue (cationic dye; MB) dye from its solution. The polyaniline nanofiber base (PNB) was synthesised by an interfacial polymerisation technique using ammonium persulphate as the oxidant and toluene as the organic solvent, and was characterised by FTIR, SEM, BET, HRTEM and XRD techniques. The HRTEM and SEM results showed that the average size of the synthesised polyaniline nanofiber base (PNB) was about 60 nm. BET revealed the enhanced surface area of polyaniline nanofiber base (PNB), i.e., 48 m2g−1 in comparison to that of conventionally synthesised polyaniline, which is only 14 m2g−1. The electric conductivity of the polyaniline nanofiber base (PNB) was reportedly lesser (2.3 × 10−2 S/cm) than the salt form of the polyaniline, measured by four probe technique. The batch-wise adsorption of MB was conducted onto the polyaniline nanofiber base (PNB), and the influence of the preliminary dye concentration, duration of contact and polyaniline nanofiber base (PNB) dose, etc., were studied. The equilibrium values of these parameters are reported as 6 mg/L, 60 min and 2 g/L, respectively. The results revealed the 91% sorption of dye onto the polyaniline nanofiber base (PNB). The experimental data were best-fitted to Pseudo-second order (R2 = 0.99) and followed Freundlich isotherm model (R2 = 0.97). On desorption, about 86% of the absorbed dye was recovered and the regenerated adsorbent could be used efficiently for three more cycles.

ELABORAREA METODEI DE USCARE AERODINAMICA A MASEI VEGETALA TOCATA

The article presents the theoretical study and elaborates the calculation methodology of the technological and constructive parameters of the aerodynamic dryers: the saltation speed of the vegetal mass particles, the speed of the thermal agent flow, the length of the dryer pipes and the duration of the moist particles contact with the thermal agent. The comparative analysis of the aerodynamic dryers was performed: with direct and vortex flow. The advantages of vortex dryers, recommended for implementation in production, are theoretically argued. In the research of the developed conical shape dryer, it has been identified a phenomenon of vortex flow parameters self-regulation to the material to be dried inside the dryer, under the condition of varying the amount of material feeding the dryer, allowing automatic creation of optimal drying conditions, when the supply of raw material and/or its humidity were changed within the studied limits. It has been demonstrated the possibility to increase up to 12-15 times the duration of contact of the raw material particles with the thermal agent and, respectively, to reduce the overall dimensions of the developed vortex dryer, compared to the known ones, which have direct air flow.

Graph modelling for tracking the COVID-19 pandemic spread

The modelling is widely used in determining the best strategies for the mitigation of the impact of infectious diseases. Currently, the modelling of a complex system such as the spread of COVID-19 infection is among the topical issues. The aim of this article is graph-based modelling of the COVID-19 infection spread. The article investigates the studies related to the modelling of COVID-19 pandemic and analyses the factors affecting the spread of the disease and its main characteristics. We propose a conceptual model of COVID-19 epidemic by considering the social distance, the duration of contact with an infected person and their location-based demographic characteristics. Based on the hypothetical scenario of the spread of the virus, a graph model of the process are developed starting from the first confirmed infection case to human-to-human transmission of the virus and visualized by considering the epidemiological characteristics of COVID-19. The application of graph for the pandemic modelling allows for considering multiple factors affecting the epidemiological process and conducting numerical experiments. The advantage of this approach is justified with the fact that it enables the reverse analysis the spread as a result of the dynamic record of detected cases of the infection in the model. This approach allows for to determining undetected cases of infection based on the social distance and duration of contact and eliminating the uncertainty significantly. Note that social, economic, demographic factors, the population density, mental values and etc. affect the increase in number of cases of infection and hence, the research was not able to consider all factors. In future research will analyze multiple factors impacting the number of infections and their use in the models will be considered.

Pup rearing: The role of mothers and allomothers in free-ranging domestic dogs

Allomaternal care (AMC) is provided to the offspring by individuals other than the genetic mother, including several seemingly altruistic behaviors such as babysitting, carrying, nursing, crèching, or huddling for thermoregulation. To determine whether there is any allomaternal care among free-ranging domestic dogs, from March 2015 to May 2019 a total of eight dog groups consisting of 19 adult females (range 2–3 females per group) that were matrilineal relatives, i.e., maternal grandmothers, aunts, daughters, sisters were observed during pup-rearing period (1st to 13 weeks of pups’ life). During the first two weeks, lactating bitches were observed to spend the most time with their own pups and suckled for almost the entire observation period (30 min). Lactating mothers started to venture out of their dens for short foraging trips when the pups were 1 week old, but it was more frequent at 3 weeks of age. From the 3rd week of kin-related pups’ life the lactating mothers were observed to wean, with a parallel shift of nursing and regurgitation for the pups done by other kin-related females showing the evidence of allonursing. The occurrence of all types of nursing activities i.e., duration of contact, nursing, feeding by regurgitation, and protection of pups was higher among the mothers than among the allomothers. In the case of biological mothers, the frequency and duration of contact, nursing and feeding by regurgitation decreased as the puppies aged, meanwhile in the case of allomothers, the frequency and duration of contact, nursing and feeding by regurgitation increased until 6 weeks of age, before switching to a decreasing trend. Allonursing in free-ranging domestic dogs was more common among older bitches i.e., maternal grandmothers. We propose four possible reasons of allonursing in the case of free-ranging dogs- 1) having excess milk perhaps due to high pup mortality allonursing may evolve as low cost behavior in free-ranging dogs, 2) allonursing may provide substantial benefits to pups regarding growth, survival, and the transfer of immune compounds, 3) insufficiency of own mother’s milk may be one of the causes of allonursing, and 4) free-ranging domestic dogs nurse each other’s pups perhaps to promote a set of affiliating and permissive relationships among the group members. As the studied groups contained matrilineal related female dogs that helped each other with allonursing, this study strongly suggests the kin selection theory especially as allonursing is highly prevalent in other, closely related, gregarious wild canids (gray wolves, golden jackals).