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Abstract: Water is a suitable medium for the Petasis-borono-Mannich multicomponent reaction. Salicylaldehyde, glyoxalic acid, glycoaldehyde and glyoxal were reacted with several boronic acids and different amines affording alkylaminophenols, 2H-chromenes, α-amino acids, α-amino alcohols and 2-hydroxylmorpholines in good to high yields. An efficient new one-pot method for the assembly of boron-heterocycles based on amino-acids, boronic acids and salicylaldehyde using water as the reaction media is presented. The mechanisms of these reactions were studied by means of DFT calculations, and the effect of solvent on the calculated energy barriers was addressed, for different aldehydes. [Copyright &y& Elsevier]

Abstract: Bovine herpesvirus 1 (BoHV-1) is widely distributed among cattle populations and has been associated with cells, fluids, and tissues collected from donor animals for use in reproductive technologies. The purpose of this study was to determine if lactoferrin would inhibit BoHV-1 in cell culture and to evaluate if embryos could develop normally when cultured in vitro with lactoferrin. In Experiment 1, lactoferrin (10mg/mL) inhibited up to 25,000 plaque forming units (PFU)/mL of BoHV-1 in Madin Darby bovine kidney (MDBK) cell culture. In Experiment 2, lactoferrin (10mg/mL) combined with cidofovir (62.5μg/mL) inhibited up to 100,200PFU/mL of virus in cell culture. In Experiment 3, following fertilization, presumptive zygotes were cultured in media containing lactoferrin (10, 5, and 2.5mg/mL). Embryonic development and quality were assessed, and embryonic viability was determined by counting the nucleated cells of developed blastocysts. While lactoferrin did not affect the nucleated cell count of the treated embryos, it did significantly decrease blastocyst development. In conclusion, lactoferrin from bovine milk can inhibit BoHV-1 in cell culture. However, supplementation of in vitro culture medium with lactoferrin inhibits blastocyst development of in vitro-produced embryos. [Copyright &y& Elsevier]

Abstract: Bovine viral diarrhea virus (BVDV) can be present in cryopreserved bovine semen and be transmitted through artificial insemination. Because BVDV can be shed in milk, the virus might also be introduced as a contaminant of milk-based semen extenders. Thus, the purpose of this study was to evaluate the epidemiologic risk of using heated, BVDV-contaminated milk to prepare semen extender. Milk was obtained from cows free of and persistently infected (PI) with BVDV. Six replicates of milk samples were processed by heating (85–92.2°C, 10min). Samples of milk collected before and after heating were assayed for BVDV. Additionally, milk was injected intravenously into eight BVDV seronegative calves to monitor for seroconversion and viral infection. Virus was not detected in any milk samples from negative animals. Virus was consistently isolated from unheated milk samples from PI cows by passage of somatic cells, ultracentrifugation, and animal inoculation. Virus was usually detected in these samples by RT-nPCR (reverse transcription nested polymerase chain reaction). In heated milk samples from PI cows, no infectious BVDV was detected using any technique, but viral RNA was detected using RT-nPCR in four of six replicates. Bovine viral diarrhea virus in milk from PI cows was inactivated by heating. Therefore, properly heated milk used in semen extenders will not result in transmission of infectious BVDV. Although RT-nPCR detected the presence of viral RNA in milk samples after heating, the virus was not infectious as demonstrated by lack of replication despite using multiple sensitive techniques. [Copyright &y& Elsevier]

Abstract: The purpose of this paper is to review scientific evidence regarding pathogens that cause infertility of bulls or that could be transmitted via bovine semen. Although several pathogens can cause male infertility and potentially be transmitted via semen, adhering to disease control recommendations provided by Certified Semen Services (CSS) and the World Organization for Animal Health (OIE) can prevent infectious male infertility and ensure that the risk of pathogen transmission via semen is negligible. Regarding bulls to be used for natural breeding, quarantine prior to herd introduction and appropriate diagnostic testing during quarantine will commonly prevent introduction of pathogens that adversely affect reproduction. [Copyright &y& Elsevier]

Abstract: The purpose of this review is to summarize bacterial, fungal, protozoan, and viral causes of reproductive dysgenesis in cattle, sheep, goats, pigs, horses, dogs, and cats. The clinical presentations of disease due to reproductive pathogens are emphasized, with a focus on assisting development of complete lists of causes that result in abortion and infertility in these species. Clinicians are encouraged to assess clinical presentation, create complete lists of differential diagnoses, obtain appropriate diagnostic samples, maximize diagnostic laboratory support, and avoid zoonotic infections resulting from reproductive pathogens of animals. The foundation of an accurate diagnosis of reproductive loss due to infectious pathogens facilitates the prudent use of immunization and biosecurity to minimize reproductive losses. [Copyright &y& Elsevier]

Abstract: Although porcine-origin trypsin will effectively remove bovine herpesvirus 1 (BHV-1) associated with in vivo-derived embryos, TrypLE™, a recombinant trypsin-like protease, has not been evaluated. In Experiment 1, 17 groups of 10 in vivo-derived embryos were exposed to BHV-1, treated with TrypLE™ Express or TrypLE™ Select (10× concentration) for varying intervals, and assayed as 2 groups of 5 embryos. TrypLE™ Select treatment for 5 and 10min (two and seven groups of five embryos, respectively) effectively inactivated BHV-1. In Experiment 2, 22 groups of 10 IVF embryos were treated and assayed. Treatment with TrypLE™ Select for 7 and 10min (six groups of five embryos each) and with TrypLE™ Select diluted 1:2 for 10min (seven groups of five embryos) was also effective. In Experiment 3, 17 groups of 10 IVF embryos were further evaluated with TrypLE™ Select undiluted and diluted 1:2 for 10min. Treatment with the diluted product was effective (18 groups of five embryos), whereas the undiluted product was not completely effective (virus isolated from 2 of 16 groups). In Experiment 4, IVF embryos were treated as described in Experiment 3 and then cultured individually or as groups of five on uterine tubal cells (UTCs) for 48h; 60% of UTC samples associated with groups of embryos and 35% of UTC associated with individual embryo samples were positive for BHV-1. Therefore, although TrypLE™ Select appeared to have promise for the treatment of in vivo-derived embryos, it cannot be recommended for treatment of in vitro-derived embryos. [Copyright &y& Elsevier]

Abstract: Fretting fatigue tests have been carried out on 7075-T6 aluminium alloy and En24 steel as a pad material to study the crack initiation behaviour. An asymptotic analysis is carried out to study the equivalence of stress state at the edge of a rectangular pad for complete contact for the Dundur’s parameters, α, β and at notch root of an associated internal angle, 2γ and subsequently a model is developed giving the stress singularity, λ −1 for the complete contact for dissimilar materials with friction. Further, a theoretical formulation is developed to predict the crack initiation angle using the stress singularity, λ −1 and the strain energy density failure criteria. The crack initiation angle experimentally obtained through the scanning electron micrographs of the failed fretting fatigue specimens are compared with the predicted crack initiation angle using the strain energy density failure criteria. The experimental observations and the theoretical results suggest that the strain energy density failure criteria can be successfully used to predict the crack initiation angle under fretting fatigue loading conditions for the complete contact case with friction. Also it is observed that the crack initiation angle in general decreases with increase in coefficient of friction at the interface. [Copyright &y& Elsevier]

Abstract: An unique fretting fatigue test rig has been designed and fabricated to characterize the fretting fatigue damage process with a facility to view the crack which is being initiated in and around the contact zone during the test. The test rig incorporates load cells for normal and friction force measurements. The complete calibration details for the custom built load cells for normal and friction force measurements are furnished. The fretting fatigue experiments have been conducted with 7075-T6 aluminium alloys to demonstrate the capability of the fretting fatigue test rig. Clear crack initiation microscopic results provided. The crack initiation cycles reduces with an increase in normal stress keeping axial stress amplitude at a constant value. Also the crack initiation cycles reduces with an increase in axial stress amplitude keeping normal stress at a constant value. The crack propagation results are also presented. [Copyright &y& Elsevier]

A prototype knowledge based system (KBS) for material selection of ceramic matrix composites (CMC) for engine components such as piston, connecting rod and piston ring is proposed in this paper. The main aim of this research work is to select the most suitable material for the automotive engine components. The selection criteria are based upon the pre-defined constraint value. The constraint values are mechanical, physical properties and manufacturing techniques. The constraint values are the safety values for the product design. The constraint values are selected from the product design specification. The product design specification values are selected from the past design calculation and some values are calculated by the help of past design data. The knowledge-based system consists of several modules such as knowledge acquisition module, inference module and user interface module. The domains of the knowledge-based system are defined as objects and linked together by hierarchical graph. The system is capable of selecting the most suitable materials and ranks the materials with respect to their properties. The design engineers can choose the required materials related to the materials property. [Copyright &y& Elsevier]

Milk and milk-based foodstuffs are considered as a primary source of nutrition to human health. Therefore, monitoring of hazardous material in powdered milk is important for the safety of public health. This study determines the concentrations of primordial radionuclides in powdered milk samples collected from the local markets of Dhaka city in Bangladesh using HPGe γ-ray spectrometry. The mean activity concentrations of 226Ra, 232Th and 40K for infant (9.6 ± 2.10, 9.0 ± 1.5 and 164.5 ± 3.7 Bq kg−1, respectively) were found comparable to the people of all other ages (7.2 ± 3.7, 7.4 ± 1.5 and 143.2 ± 3.9 Bq kg-1, respectively). Based on the typical consumption characteristics of powdered milk, the mean annual effective doses were found below the FAO/WHO (1995) and ICRP (2007) recommended limit of 1 mSv y-1 for public exposure, in all investigated age groups (<2 y - >17 y). On the other hand, the doses for infant show close to the UNSCEAR (2000) reference ingestion dose constraints of 290 μSv y−1, which may indicate a non-negligible concern for the infants' health. The carcinogenic risks due to the ingestion of radionuclide show to be 6.4 × 10−4 (0–72 years) and 5.4 × 10−4 (>2 years) are significantly less than the ICRP (2006) suggested cancer risk factor of 2.5 × 10−3 based on the annual dose limit of 1 mSv for general public, thus discarded the radiation hazards via the consumption of local or imported powdered milk in Bangladesh. Overall, the measured data may help to establish national rules and regulations on powdered milk relating to radiological protection for the general people of Bangladesh. • Powdered milk was assessed for NORM contents and is the first study in Bangladesh. • 226Ra, 232Th, and 40K concentrations were found comparable for all age groups. • The mean annual effective doses show below ICRP ref. of 1 mSv y−1 for all ages. • Cancer risks due to ingestion of radionuclide show below ICRP ref. of 2.5 × 10−3. • Data will help to establish radiological protection guidelines on powdered milk. [ABSTRACT FROM AUTHOR]

Middle ear adenomatous neuroendocrine tumours (MEANTs) are rare, unpredictable tumours. Although most MEANTs are characterized by a benign biological behaviour and indolent growth pattern, some studies have reported locally invasive and metastastic disease. Currently, the optimal management strategy for MEANTs remains subject of debate. The aim of this study is to review the literature on MEANTs with focus on its clinical characteristics, treatment strategies and outcome. A systematic review was conducted using PubMed, Embase and Cochrane databases. A total of 111 studies comprising 198 patients with MEANT were included. Treatment modalities comprised surgery (90%), surgery with adjuvant radiotherapy (9%) and palliative (chemo)radiotherapy in (1%). Local recurrence was observed in 25% of the patients and 7% of the patients developed metastasis, over a median period of 5.7 years (range 7 months - 32 years). Twelve of 13 patients (92%) who developed metastases had a local recurrence. Four patients (2%) died of MEANT: three due to distant metastases and one due to extensive local recurrence. Reliable histopathologic predictors of outcome could not be identified. These findings indicate that the clinical presentations of MEANT vary substantially, the overall recurrence rate is considerable and initial local tumour control is paramount. Because of the unpredictable clinical course, prolonged follow-up is warranted. [ABSTRACT FROM AUTHOR]

Attempts to estimate the magnitude of, and changes in the second economy in Tanzania, to establish the extent to which official statistics misstate actual production of goods and services. Defining the second economy; Estimating the size of the second economy; Empirical results.

Anti-obesity drugs in the amphetamine (AMPH) class act in the brain to reduce appetite and increase locomotion. They are also characterized by adverse cardiovascular effects with origin that, despite absence of any in vivo evidence, is attributed to a direct sympathomimetic action in the heart. Here, we show that the cardiac side effects of AMPH originate from the brain and can be circumvented by PEGylation (PEGyAMPH) to exclude its central action. PEGyAMPH does not enter the brain and facilitates SNS activity via theβ 2 -adrenoceptor, protecting mice against obesity by increasing lipolysis and thermogenesis, coupled to higher heat dissipation, which acts as an energy sink to increase energy expenditure without altering food intake or locomotor activity. Thus, we provide proof-of-principle for a novel class of exclusively peripheral anti-obesity sympathofacilitators that are devoid of any cardiovascular and brain-related side effects. • PEGylated amphetamine (PEGyAMPH) does not enter the brain, nor has behavioral effects • PEGyAMPH promotes weight loss, by coupling thermogenesis to heat dissipation • PEGyAMPH is a sympathofacilitator , requiring β 2 -adrenoceptor function • PEGyAMPH is cardioprotective, unless directly delivered into the brain PEGyAMPH is a brain-sparing modified amphetamine that is a cardioneutral anti-obesity drug. Unlike amphetamines, which act in the brain to increase satiety and locomotion, PEGyAMPH couples thermogenesis to heat dissipation, activating a whole-body energy sink by simultaneously promoting vasodilation and facilitating the activity of sympathetic neurons. [ABSTRACT FROM AUTHOR]

This work reports on the structural, electrical and electrochemical properties of Zn doped LiNi 0.5-x Zn x Mn 1.5 O 4 (x = 0.0, 0.05, 0.1 and 0.2) porous microspheres cathode materials obtained by a hydrothermal route followed by low-temperature annealing. Structural properties are investigated by X-ray diffraction (XRD), nuclear magnetic resonance (NMR) spectroscopy; scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman, and Fourier transform infrared (FTIR) spectroscopy. The XRD patterns and NMR studies further demonstrate the successful incorporation of Zn into the spinel structure. SEM reveals morphology with porous spheres with a size range of 0.2 μm – 1 μm. Temperature dependent electrical conductivity was measured by impedance spectroscopy. The activation energies of total conductivity are determined as 0.41, 0.41, 0.47, and 0.48 eV for x = 0, 0.05, 0.1, and 0.2, respectively. Influence of Zn doping on the grain, grain boundary and total conductivities of LiNi 0.5-x Zn x Mn 1.5 O 4 were analyzed through brick-layer model. The grain conductivity increases with Zn content, whereas the total conductivity increases till x = 0.1. Overall, electrical properties of LiNi 0.5-x Zn x Mn 1.5 O 4 are governed by grain boundary conduction. Increasing the Zn content up to x = 0.1 in LiNi 0.5-x Zn x Mn 1.5 O 4 leads to an increment in specific capacity at a 1C rate. Among them, the LiNi 0.4 Zn 0.1 Mn 1.5 O 4 exhibits a high discharge capacity of 114 mAh g−1 at 1C with capacity retention of 91.5% after 50 cycles. We also investigated the effect of Zn doping on Li+ ion diffusivity and observed improved Li+ ion diffusion (7.4⋅10−13 cm2 s−1) for LiNi 0.4 Zn 0.1 Mn 1.5 O 4. Based on these electrochemical studies it is proposed that this material can be utilized as a cathode in Li-ion batteries for high-power applications. [ABSTRACT FROM AUTHOR]

Abstract A highly-stressed shaft pillar is prone to large seismic events, falls of ground and rockbursts, which may cause injuries and loss of production, especially in weak geotechnical zones. It is thus important to identify weak geotechnical zones in order to mitigate risks. In this study, we present integrated studies (underground mapping, petrology, rock mechanics and high-resolution microseismicity analysis) to understand the different geotechnical zones in the shaft pillar of Cooke 4 mine in South Africa. The footwall of the remnant shaft pillar comprises the Upper Elsburg reef of the Mondeor Formation, while the Ventersdorp Contact Reef (VCR) of the Venterspost Formation and soft/weak lavas of the Westonaria Formation form the hangingwall. Results from underground mapping and microscopic analysis show that the shaft pillar is composed of quartzites, pebbly quartzites, argillaceous quartzites and conglomerates. Underground mapping further shows that the shaft pillar is characterized by several discontinuities, which vary from minor to macro scale fractures. Laboratory uniaxial compressive strength (UCS) tests indicate that quartzite has the strongest strength, followed by pebbly quartzite, argillaceous quartzite and lastly, conglomerate. Analysis of high-resolution acoustic emissions (AEs) clusters indicates that the majority of AEs are associated with the mining stope faces. The clusters show the formation of Ortlepp shears ahead of the stope, which is caused by the excavation-induced stress field. Microseismic data further reveal that the fracture turning-point occurs in the soft strata (weak hangingwall lavas). The integration of these datasets has allowed us to develop the fracture model for different geotechnical zones, which concurs with previous models developed for the similar underground environment (i.e., weak/soft lava hangingwall and quartzite/conglomerate footwall). This has major implications for future mining, support, production and safety. [ABSTRACT FROM AUTHOR]

Abstract: The reproductive impact following controlled introduction of animals persistently infected (PI) with bovine viral diarrhea virus (BVDV) was evaluated in BVDV-naive heifers. Heifers were randomly allocated into two groups: an unexposed control herd (n = 34) and a herd exposed to five persistently infected (PI) animals for 7 mo, beginning 50 days before the breeding season (n = 34). Initiation of the BVDV-challenge was timed to mimic either direct contact with PI calves born in the previous calving season or accidental introduction of PI herd additions prior to the breeding season. The PI animals represented BVDV Types 1a (n = 3), 1b (n = 1) and 2 (n = 1). Two BVDV-free, seropositive bulls were used in each group for 78 days breeding seasons. In both groups, 33 of 34 heifers became pregnant, with similar distribution of fetal ages. Two heifers in each group aborted (etiology undetermined). In addition, one calf was born dead and one calf died 3 days post-partum in the BVDV-exposed group. One calf in the unexposed group died 4 mo post-partum. No calves, including the stillborn calf and the two calves that died prior to weaning, were persistently infected with BVDV. In summary, introduction of PI cattle to a group of BVDV-naive heifers 50 days prior to the breeding season did not negatively impact reproductive performance. To the contrary, the active immunity that developed following field exposure to BVDV provided effective reproductive and fetal protection during the breeding season and subsequent gestations, despite continuous exposure to PI animals until approximately midgestation. Although BVDV can have potentially devastating reproductive effects, timing of infection is a critical determinant in the outcome of a BVDV infection. A controlled breeding season with introduction of herd additions at less critical reproductive time points can mitigate the negative reproductive health consequences of BVDV. [Copyright &y& Elsevier]

Abstract: Bovine viral diarrhea virus (BVDV) has been shown to be associated with single transferable in vivo–derived bovine embryos despite washing and trypsin treatment. Hence, the primary objective was to evaluate the potential of BVDV to be transmitted via the intrauterine route at the time of embryo transfer. In vivo–derived bovine embryos (n=10) were nonsurgically collected from a single Bos tarus donor cow negative for BVDV. After collection and washing, embryos were placed into transfer media containing BVDV (SD-1; Type 1a). Each of the 10 embryos was individually loaded into an 0.25-mL straw, which was then nonsurgically transferred into the uterus of 1 of the 10 seronegative recipients on Day 0. The total quantity of virus transferred into the uterus of each of the 10 Bos tarus recipients was 878 cell culture infective doses to the 50% end point (CCID50)/mL. Additionally, control heifers received 1.5×106 CCID50 BVDV/.5mL without an embryo (positive) or heat-inactivated BVDV (negative). The positive control heifer and all 10 recipients of virus-exposed embryos exhibited viremia by Day 6 and seroconverted by Day 15 after transfer. The negative control heifer did not exhibit a viremia or seroconvert. At 30 d after embryo transfer, 6 of 10 heifers in the treatment group were pregnant; however, 30 d later, only one was still pregnant. This fetus was nonviable and was positive for BVDV. In conclusion, the quantity of BVDV associated with bovine embryos after in vitro exposure can result in viremia and seroconversion of seronegative recipients after transfer into the uterus during diestrus. [Copyright &y& Elsevier]

Abstract: The objective was to determine the average amount of bovine viral diarrhea virus (BVDV) associated with single in vivo-derived and in vitro-produced bovine embryos following recommended processing procedures for embryos. In vivo-derived and in vitro-produced bovine embryos at 7d post-fertilization were exposed (for 2h) to 2×105–7 cell culture infective dose (CCID50)/mL of SD-1 (a noncytopathic, Type 1a strain of BVDV), and then washed according to International Embryo Transfer Society (IETS) guidelines prior to testing. Of the 87 in vivo-derived embryos tested, 27% were positive for virus by quantitative polymerase chain reaction (qPCR). The range in amount of virus associated with 99% of the contaminated embryos was ≤6.62±1.57copies/5μL; 90% of the contaminated embryos had ≤4.64±1.57viralcopies/5μL of embryo-associated virus, using tolerance intervals (P <0.05). The SEM was 0.33 and the mean of averages was 1.12/5μL. Of the 87 in vitro-produced embryos, 42% were positive for virus. The range in amount of virus associated with 99% of the contaminated embryos was ≤3.44±0.89copies/5μL; 90% of the contaminated embryos had ≤2.40±0.89viralcopies/5μL of embryo-associated virus using tolerance intervals (P <0.05; S.E.M. was 0.14 and the mean of averages was 0.55/5μL). Therefore, although many embryos were positive for virus, there were limited numbers of copies, thereby posing doubt regarding their potential for contamination following embryo transfer. [Copyright &y& Elsevier]

Abstract: The objectives of this study were to develop techniques to detect BVDV associated with single or small groups of bovine embryos contained in small aliquots of medium using either virus isolation (VI) or real time quantitative polymerase chain reaction (RT-QPCR) assays. In vivo-derived and in vitro-produced bovine embryos at 7 d post-fertilization were exposed to SD-1, a high affinity strain of BVDV, for 2h and then processed according to the International Embryo Transfer Society (IETS) guidelines prior to testing. Groups of five or two in vivo-derived embryos, and single in vivo-derived embryos, were VI positive for BVDV 100, 50, and 33% of the time, and were RT-QPCR positive 100, 75, and 42% of the time, respectively. The virus was detected by the VI technique in all of the groups of five or two in vitro-produced embryos and in all of the single in vitro-produced embryos, and it was detected in 100, 80, and 50%, using RT-QPCR. Techniques for RT-QPCR were sufficiently sensitive to detect 10 copies of viral RNA in a sample and to detect BVDV associated with single embryos. Application of this new technology, RT-QPCR, will facilitate additional studies to further assess the risk of transmission of BVDV through embryo transfer. [Copyright &y& Elsevier]

Bovine viral diarrhea virus (BVDV) is a significant pathogen that can be shed in the semen of infected bulls. Thus, screening for BVDV in semen of bulls is recommended prior to their entry into an artificial insemination center. No previous research has compared the analytical sensitivity of reverse transcription-nested polymerase chain reaction (RT-nPCR) and virus isolation assays for detection of BVDV in semen from an infected bull. Therefore, the goals of this research were to compare the analytical sensitivity of RT-nPCR and virus isolation assays for BVDV in semen and to apply these assays to determine the prevalence in the Southeastern United States of bulls that lack viremia yet shed BVDV in semen. Semen collected from a bull that was persistently infected with BVDV was serially diluted (1/10) in semen from uninfected bulls and frozen in liquid nitrogen as raw, partially extended or fully extended semen. Subsequently, samples of semen were assayed by virus isolation and RT-nPCR. Viral detection was more sensitive in extended semen samples than in raw semen samples and more sensitive by RT-nPCR than virus isolation. After this evaluation of analytical sensitivity, serum and semen were collected from 558 post-pubertal bulls in our region. These samples were tested for BVDV by virus isolation. Partially extended semen was also assayed for BVDV by RT-nPCR. All samples were negative by all assays for BVDV. The application of analytically sensitive assays reveals a very low prevalence (≤0.54%) of BVDV in semen from bulls in the Southeastern United States. [Copyright &y& Elsevier]

The presence of fault gouge and the generation of wear material between two sliding rock surfaces plays a critical role in slip weakening and propagation of ruptures along underground brittle shear fractures forming ahead of tabular excavations in deep and high stress gold mining. We performed two types of friction experiments: one with a fault gouge layer between two sliding surfaces, and the other without a fault gouge layer 'rock-on-rock', both under room dry conditions at slip velocities ranging from ~1.0 mm/s to 1200 mm/s. These friction experiments revealed a remarkable difference in the frictional weakening behaviour, e.g., rock-on-rock friction experiments show weakening behaviour at lower slip velocity (~5 mm/s) and generally has lower frictional strength than those with the intervening fault gouge between sliding surfaces. This study shows that the existence of the fault gouge layer between sliding rock surfaces delays the onset of fault weakening (i.e., slip weakening displacement of gouge layer experiments is larger compared to rock-on-rock experiments). It is proposed that flash heating may be the main active weakening mechanism within both our gouge and rock-on-rock experiments, and provides a feasible account for the observed weakening. The observed slip weakening displacement (D c) differences may be attributed to the presence of a gouge layer between sliding surfaces, which has many more contacts during sliding compared to rock-on-rock experiments, thus reducing the average slip velocity per contact, consequently, the potential for activation of flash heating which delays the onset of weakening. Here we suggest that we may be able to describe brittle shear fracture rupture propagation process along underground brittle shear zones by conducting low, intermediate and high slip velocity friction experiments with and without an intervening fault gouge between sliding rock surfaces. These findings should have important implications for the modelling of rupture propagation processes in underground shear zones, a phenomenon that influences the severity of rockbursts, and hence the safety of mine workers and mining operations. [ABSTRACT FROM AUTHOR]