Hammer Percussion Research Articles

Design and Experimental of the Soil Removal Device for Root-Soil Complex of Gentian Imitating the Percussion of Woodpeckers.

A soil removal device for the root-soil complex of Gentian imitating the percussion function of a woodpecker was designed to improve the soil removal efficiency of harvesting devices for rhizome-type traditional Chinese herbal medicines. Based on the physical parameters of roots and the root-soil complex of Gentian, the structure parameters of the striking arm and the actual profile of the cam are determined according to the physical parameters when the woodpecker knocks on the tree. The key parameters that affect the working performance of the soil removal device and their suitable value ranges have been identified through the impact test and analysis of the root-soil complex of Gentian. The mass of the striking hammer, the swing angle of the striking arm, and the rotation speed of the cam were taken as the experimental factors and the soil removal rate and the energy consumption per hammer percussion were taken as the experimental indicators. The ternary quadratic orthogonal regression combination experiment was carried out using Design-Expert. The regression model of the influence factors and evaluation indicators was established through the analysis of variance. The interaction effects of the influence factors on the indicators were analyzed using the response surface method. Using multiobjective optimization method, the optimal parameter combination was obtained as that of the mass of the striking hammer of 0.9 kg, the swing angle of the striking arm of 47°, and the rotation speed of the cam of 100 r/min, then the soil removal rate was the maximum and the energy consumption of single-hammer knocking was the minimum, with the values of 89.12% and 31.21 J, respectively. This study can provide a reference for the design and optimization of soil removal devices for rhizome-type traditional Chinese herbal medicines.

Experimental and Numerical Simulation Study on the Mechanism of Fracture-Increasing and Permeability-Increasing in Granite Pore Walls by the Air DTH Hammer Percussion Drilling

Air DTH (Down-The-Hole) hammer percussion drilling (vibration percussion drilling) has proven to be a highly efficient geothermal drilling technique, and percussion fractures near the wellbore benefit geothermal energy development in many ways (such as hydraulic fracturing, perforation, etc.). However, no research has been done on the mechanism of fracture-increasing and permeation-increasing in granite pore walls by air DTH hammer percussion drilling. This article: (1) using an air drilling test device, an air DTH hammer whole bit impact rock fragmentation test was conducted on granite in an atmospheric environment; (2) dyeing experiments, CT scanning, and 3D reconstruction modeling were used to characterize and identify wellbore cracks; (3) research the strength, porosity, and permeability changes of granite wellbore through mechanical and permeability testing experiments; and (4) numerical simulation of impact stress waves using particle flow code (PFC) 6.0 software to demonstrate the rationality of impact experimental results. The results show that the air DTH hammer impact can induce micro-cracks in the wellbore, and the distribution of cracks is regionalized, mainly due to the attenuation of the impact stress wave. The numerical results are consistent with the experimental results. The average strength of granite decreased by 16.5%, the average porosity increased by 9.5%, the average permeability increased by 63.3%, the porosity increased from 0.0025% to 0.03%, and the porosity increased by about 12 times under the air DTH Hammer percussion drilling. The above results provide the theoretical basis and experimental proof for the ability of air DTH hammer drilling to produce wellbore cracks and improve wellbore permeability. The presented experimental results can be a useful reference for building numerical models.

Composite embedded track structure considering temperature dependent characteristics for rolling noise reduction of inter-city railway system

Intercity railway will generate strong noise when passing through the surrounding residents, among which rolling noise is the main noise source and is difficult to control. A composite embedded track structure containing polymer material was fabricated to analyze its damping and rolling noise reduction characteristics. The damping characteristics of polymer materials of embedded track were tested by dynamic thermo-mechanical analyzer (DMA Q800). The frequency response function (FRF) of the embedded track system is tested by force hammer percussion method. The vibration of the embedded track is simulated by the the 2.5-dimensional finite element method (2.5D FEM) considering damping characteristics obtained by material test of DMA Q800. The sound radiation model of embedded track is developed by using 2.5-dimensional sound boundary element method (2.5D BEM). The model is verified by the test. The FRF, track decay rate, and wheel-rail force at different temperatures are analyzed. With the decrease of temperature, the elastic modulus and loss factor of polymer material of embedded track increase, which will affect the above results. Sound directivity and effect on wheel-rail noise reduction of embedded track have been studied. The results show that the composite embedded track has good damping characteristics and noise reduction performance. Sound sensitivity analysis of loss factors of the three polymer materials of embedded track is carried out to improve embedded track noise reduction capability.

Lithic technological strategies of Late Pleistocene hominins in the Daoshui River valley, Hunan province, central South China

The Late Pleistocene is a crucial period of dramatic changes in lithic technologies as well as interactions between modern humans and other archaic human groups. In this paper, we describe the technological analysis of lithic assemblages collected from 28 newly discovered Paleolithic sites along the Daoshui River, a tributary of the Lishui River (itself a tributary of Yangtze River) in northern Hunan Province, central South China. Luminescence dating of several sites in this region has provided a general Late Pleistocene age range for lithic assemblages. Technologically, high quality raw materials are predominantly exploited (e.g., chert and siliceous slate) and direct hard hammer percussion predominates which lacks the classic Levallois technology though conceptually, some specimens do exhibit a certain degree of volumetric control and share other common features with prepared cores, here we tentatively define them as “simply prepared cores.” Small flakes and flake tool production plays a primary role in the overall technological strategy, accompanying a small proportion of large flakes and Large Cutting Tools production. Our examination of lithic technologies in the region clearly contrasts with the traditional view of South China being characterized by a simple cobble tool industry over the course of the Pleistocene period. We further discuss the issue of the Middle Paleolithic in China, as well as the ecological adaptations of hominins in the Daoshui River valley within a Late Pleistocene climatic context.

Skill and Core Uniformity: An Experiment with Oldowan-like Flaking Systems

ABSTRACT The Oldowan is the archaeological record’s oldest consistent evidence of hominin technical behavior. First appearing ∼2.6 Ma in East Africa, the Oldowan is characterized by simple core and flake technology using direct hard hammer percussion. Archaeologists debate whether Oldowan assemblages are uniform and what role hominin cultural abilities played in generating these assemblages. To improve existing methods for studying Oldowan technical uniformity, we conducted experiments involving 23 novices and one expert knapper. Subjects made simple stone tools under two different instructional conditions (observation-only and direct active instruction) over two hours. We used the resulting cores to track flaking efficiency, reduction intensity, and knapping errors. We find significant differences in the expert and novice core uniformity. Direct active teaching increased core flaking efficiency and reduced knapping errors. Comparisons between our experimental results and an Oldowan sample from Gona, Ethiopia, show core variability patterns that match our expert and actively taught novices.

Possibility to apply unified methodology in vibration analysis for long lasting and impulse sources, in terms of influence on people in buildings

The present work addresses the problem of unified methodology use for vibration analysis caused by various anthropogenic sources. The experimental part of the paper contains analysis and results comparison of the vibration, induced by freight train passages and hammer percussion. Ground vibrations are important for the civil engineering objects condition since the vibration induced by train is transmitted through the ground to the foundation and structure. Ground vibration can also be a source of disturbance for the residents. However, various factors cause vibration that varies in both intensity and frequency measures. The analysis of vibration timelines, running RMS and Fourier spectra are applied. The major part of the dissertation is the analysis of RMS accelerations and velocities in one-third octave frequency bands in 1 to 80 Hz spectrum, and comparison to the background vibration noise, recorded in the same localisation. The different values of time-window observation are applied to analyse the results. The results of long lasting cargo-induced vibrations are less dependent on time-window duration than the results of impulse-induced vibrations. The acceleration and velocity analysis results are compared to the literature data concerning the ground vibration caused by railway transport and mining activity. The paper indicates the possibility to apply unified methodology for vibration analysis caused by both long-lasting sources, as trains and short-lasting ones, as industrial blasts or mine tremors. The results indicate an optimal time window for vibration measurement that would enable to automate vibration monitoring.

Regulation Mechanism of the Shock Waves in a Pentamode Lattice-Ring Structure Subjected to Collision

This paper hopes to explore the application potential of pentamode materials in the field of shock protection. Hammer percussion tests revealed that the peak strain of the inner-ring front shock surface of the pentamode lattice-ring structure is 103.9% of that of the inner-ring rear shock surface. According to the simulation results, for a solid ring of equal mass made of the same base material, the ratio mentioned above reaches 3385.7%. Compared with the solid ring of equal mass made of the same base material, the pentamode lattice-ring structure saw a decline of 65.5% in the peak strain of its inner-ring front shock surface. The distribution laws of the group velocity characterizing energy-flow characteristics were discovered by calculating cell dispersion curves in various layers of the pentamode lattice-ring structure. The laws governing the effects of cellular structure parameters on group velocity anisotropy and pentamode characteristic parameters were also revealed. It was found that the deflection angle of the energy-flow vector is positively correlated with group velocity anisotropy and that the effects of pentamode characteristic parameters π and μ on the deflection angle of the energy-flow vector vary greatly in different value ranges. The deflection angle of the energy-flow vector has a decisive effect on the protection performance of the pentamode lattice-ring structure. The conclusions of this study can provide some theoretical support for the shock protection of submarine structures.

Acheulean Diversity in Britain (MIS 15-MIS11): From the Standardization to the Regionalization of Technology

The appearance of the Acheulean and the production of new bifacial tools marked a revolution in human behavior. The use of longer and complex operative chains, with centripetal and recurrent knapping, adapted to different raw materials, created long useful edges, converging in a functional distal end. How and why these handaxes vary has been the subject of intense debates. Britain provides a clearly defined region at the edge of the hominin occupied world for discussing variation in Acheulean assemblages. The environmental changes from MIS 15 to MIS 11 are significant in understanding population change, with probable breaks in evidence during MIS 14 and MIS 12, followed by several sites during the long stable climate of MIS11c. In this latter period, different Acheulean technological expressions appear to coexist in Britain. This paper draws together different studies, combining technology and geometric morphometrics to analyze handaxes from six British sites: Brandon Fields, Boxgrove (Q1B), High Lodge, Hitchin, Swanscombe (UMG), and Elveden. Compared to the earlier Acheulean of MIS 15, the assemblages of MIS 13 show increased standardization and the use of soft hammer percussion for thinning mid-sections and butts of tools, or sharpening tips through tranchet removals. Although there is regional population discontinuity through MIS12 there is no evidence of a marked change in technology after this glacial period. Rather, there is a development towards more intense shaping with the same underlying techniques, but with flexibility in imposed handaxe form. From MIS11 there appear to be distinctive localized traditions of manufacture, which suggest that a recognition of place and territories had developed by this time. These are expressed over medium time-scales of several thousand years and have significance for how we view cultural expression and transmission.

THE UPPER PALAEOLITHIC OF CHURCHFIELDS, FISHERTON: 160 YEARS IN THE MAKING

Researchers of museum collections owe a great debt of gratitude to those responsible for curating the collections; however, staff may frequently remain innocently unaware of significant contents within the accessions. Such is a group of flint artefacts in Salisbury Museum, Wiltshire, which were found in 1860 on the outskirts of the city. The collection was rediscovered during unrelated archaeological research and comprises a series of blades, which include refitting components, demonstrating that the artefacts came from undisturbed prehistoric contexts. The blade blanks had been removed from opposed platform cores, using careful core preparation and soft hammer percussion. These characteristics can be most closely paralleled by Upper Palaeolithic Federmesser industries in Europe, which date from the end of the Last Glaciation. The existence of the Upper Palaeolithic was unrecognised at the time the artefacts were found, since when two other contemporary sites have been identified in the River Avon valley as well as others across the country. The newly recognised addition extends the distribution of Upper Palaeolithic activity further up the River Avon valley to Salisbury, where five rivers congregate, providing a convenient point for further dispersal. The finding also mirrors patterns of occupation on well-drained terrace bluffs overlooking the floodplain. Research results have yielded significant data, 160 years after the collection’s discovery, expanding current knowledge of the Upper Palaeolithic in the River Avon valley and demonstrating the continued value and potential of collections in our museums.

Kinetics of stone tool production among novice and expert tool makers.

As is the case among many complex motor tasks that require prolonged practice before achieving expertise, aspects of the biomechanics of knapping vary according to the relative experience/skill level of the practitioner. In archaeological experiments focused on the production of Plio-Pleistocene stone tools, these skill-mediated biomechanical differences have bearings on experimental design, the interpretation of results, and lithic assemblage analysis. A robust body of work exists on variation in kinematic patterns across skill levels but less is known about potential kinetic differences. The current study was undertaken to better understand kinetic patterns observed across skill levels during "Oldowan," freehand stone tool production. Manual pressure data were collected from 23 novice and 9 expert stone tool makers during the production of simple stone flakes using direct hard hammer percussion. Results show that expert tool makers experienced significantly lower cumulative pressure magnitudes and pressure-time integral magnitudes compared with novices. In expert knappers, digits I and II experienced similarly high pressures (both peak pressure and pressure-time integrals) and low variability in pressure relative to digits III-V. Novices, in contrast, tended to hold hammerstones such that pressure patterns were similar across digits II-V, and they showed low variability on digit I only. The similar and consistent emphasis of the thumb by both skill groups indicates the importance of this digit in stabilizing the hammerstone. The emphasis placed on digit II is exclusive to expert knappers, and so this digit may offer osteological signals diagnostic of habitual expert tool production.

Новая интерпретация каменной индустрии местонахождения Сай Джанурпа (Восточный Прикаспий)

The central geographical position of the Caspian region plays a key role in understanding the historical processes which took place in the territory of Central Asia. One of the important geological factors that influenced the processes of settlement in this region by ancient populations is the transgressive-regressive variability of the Caspian sea level and access to fresh water. There are dozens of Early Holocene sites on the Krasnovodsk Peninsula (Eastern Caspian), most of them being surface complexes. The interpretation of these complexes has so far been controversial due to the lack of stratigraphic context and absolute dating. Purpose. This paper analyzes the techno-typological characteristics of lithic tool assemblages assigned to Early Holocene industries from Eastern Caspian site Sai Djanurpa. The article also discusses the links of how the dynamics of the ancient shores of the Caspian influenced settlement dynamics in the region. Results. The conducted detailed techno-typological analysis of the lithic collection of Sai Djanurpa allowed to discern two distinct complexes. The two complexes defined by different technological and typological characteristics: types of chips, types of tools and metric indicators. The first complex is characterized by the exploitation of chalcedony flint for the production of blades by soft hammer percussion, by borer, end-scraper and retouched flakes in the toolkit. The second complex is associated with the use of chalcedony, sandstone and flint for the production of microbladelets by the pressure technique, from conical and frontal cores. The toolkit of the second set of complexes is characterized by bifacial narrow points, burins, ventral retouched microblades and micro-scrapers. Conclusion. Based on the analysis of the lithic assemblages, the geomorphological position of the site and the paleogeographic condition of the Caspian region, the authors assume that two different populations with two different material cultures inhabited the Sai Djanurpa site during the final Pleistocene – early Holocene and the middle Holocene.

New discoveries from the early Late Pleistocene Lingjing site (Xuchang)

The applicability of the three stage Paleolithic sequence (Lower, Middle, Upper) in eastern Asia that is used in the western Old World has long been a debated issue. The crux of the discussion is whether a distinct “Middle Paleolithic” (“MP”) is present in the eastern Asian record, especially north China. Recently, the artifacts from the Lingjing site (2005–2016), in northern China, have been argued to be potential representative of a “Chinese Middle Paleolithic” (“CMP”). In this paper, we introduce a thorough analysis on a newly discovered lithic assemblage from the 2017 excavation of the Lingjing site. We found that simple free-hand hard hammer percussion is the dominant core reduction strategy with only a very small frequency of atypical, bi-conical discoidal cores. When considering other contemporary sites in northern China (e.g., Xujiayao and Banjingzi), Lingjing belongs to a small tool tradition that is widespread throughout northern China. The Lingjing artifacts do display some obvious differences in core reduction and lithic retouching techniques from those typical of the Lower/Early Paleolithic (or Mode 1) assemblage pre-40 ka in the Chinese Paleolithic. The diversity of characteristics of lithic technology from Lingjing and other contemporary sites in north China show the complexity of the Chinese Early Paleolithic, rather than a simple monotonous stone tool tradition.

Comb Ware culture in Lithuania: new evidence from Šventoji 43

Šventoji 43 is one of eight Comb Ware culture sites known in Lithuania at present. The site was excavated in 2013 and 2014 and revealed a homogeneous pottery assemblage, which was classified as Comb Ware and was radiocarbon dated to 3900–3650 cal BC. As a result of this dating, it has been found that Comb Ware is the oldest pottery type to have been produced in coastal Lithuania. In fact, the pottery assemblage of Šventoji 43 also suggests that Comb Ware originates from a distinct phase in the pottery sequence of coastal Lithuania that both predates all other phases from Šventoji pottery bearing sites and has not been previously recognised in other assemblages. Zooarchaeological analysis has revealed that the site was occupied during the early spring and mostly used for fishing zander and pike in the lagoonal lake and for hunting seals and forest game. The unique character of the flint industry, which combined hard hammer percussion and bipolar knapping that resulted in the production of microliths on irregular blades, suggests that the local Šventoji 43 community had Mesolithic roots. Furthermore, this evidence supports the hypothesis that Comb Ware had reached Lithuania through intense contact between East Baltic hunter-gatherers rather than due to a mass migration of the population from the Northeastern Baltic. The much wider distribution of Finno-Ugric hydronyms, compared to that of Comb Ware sites gives an impression that some other Subneolithic pottery types in addition to Comb Ware might have been produced by Finno-Ugric speaking people.

Sounding of subsurface concrete defects using frequency response of flexural vibration

Standard sounding procedures such as hammer percussion and chain drag can be used to locate subsurface concrete defects, but are often subject to the individual judgement and ear of trained inspectors. However, defect depth information can be difficult to gauge by ear alone. By recording audio and analyzing the frequency content of sounding via hammer percussion, a single- and triple-link chain drag, and a novel speaker-based excitation procedure, simulated defects in concrete test slabs were detected. The speaker-based method shows the capacity to detect a similar number of defects as chain drag methods, though it is slightly less effective than the hammer method. The duration and type of the acoustic signal used by the speaker to induce vibration are important factors in performance of the speaker-based method. The detectability of a defect via all methods tested depended largely on the ratio of defect depth to defect lateral dimensions; defect detectability was shown to drop after this ratio exceeded about 0.35.

Discovery of circa 115,000-year-old bone retouchers at Lingjing, Henan, China.

Most Chinese lithic industries dated between 300,000 and 40,000 are characterized by the absence of Levallois debitage, the persistence of core-and-flake knapping, the rarity of prepared cores, their reduction with direct hard hammer percussion, and the rarity of retouched flakes. Here we report the discovery of seven bone soft hammers at the early hominin Lingjing site (Xuchang County, Henan) dated to 125,000–105,000. These artefacts represent the first instance of the use of bone as raw material to modify stone tools found at an East Asian early Late Pleistocene site. Three types of soft hammers are identified. The first consists of large bone flakes resulting from butchery of large herbivores that were utilized as such for expedient stone tools retouching or resharpening. The second involved the fracture of weathered bone from medium size herbivores to obtain elongated splinters shaped by percussion into sub-rectangular artefacts. Traces observed on these objects indicate intensive and possibly recurrent utilization, which implies their curation over time. The last consists of antler, occasionally used. Lingjing bone tools complement what we know about archaic hominin cultural adaptations in East Asia and highlight behavioural consistencies that could not be inferred from other cultural proxies. This discovery provides a new dimension to the debate surrounding the existence of the Middle Palaeolithic in the region. The attribution of East Asian sites to the Middle Palaeolithic assumes that cultural traits such as the Levallois method represent evolutionary hallmarks applicable to regions of the world different from those in which they were originally found. Here, we promote an approach that consists in identifying, possibly from different categories of material culture, the original features of each regional cultural trajectory and understanding the behavioural and cognitive implications they may have had for past hominin populations.

Caractérisation de l’industrie lithique de la fin du Néolithique, dans le bassin de la Seine (de la deuxième moitié du IVe millénaire à la fin du IIIe millénaire av. J.-C.)

Cet article présente une synthèse sur l’industrie lithique du Néolithique récent et final dans le bassin de la Seine (entre 3500 et 2100 avant notre ère). Son objectif est de distinguer l’industrie lithique du Néolithique récent de celle du Néolithique final et, plus largement, de préciser la définition des groupes culturels, leur localisation et leur chronologie par l’étude du mobilier lithique en contexte domestique et sépulcral. La première étape de la caractérisation porte sur les modalités de l’approvisionnement, généralement réalisé à proximité des occupations durant le Néolithique récent et final. L'importation de matières premières suit une même tendance, sur deux aspects, le sens de circulation des pièces en silex secondaire et tertiaire mais aussi la forme sous laquelle ces produits circulent. Le Néolithique final se distingue par une diffusion d’artefacts en roche verte et en silex du Turonien supérieur de la région du Grand-Pressigny. Au Néolithique récent, la production laminaire présente certaines caractéristiques au niveau du type de percussion utilisé (indirecte et directe tendre) mais aussi de la répartition géographique de ces techniques et sur le statut des produits laminaires en contexte sépulcral. Plusieurs indices suggèrent que le ralentissement de la production laminaire domestique débute à partir du Néolithique final. Cette période se distingue aussi par une diversification de l'outillage et par l’existence d’une production d’éclats par débitage centripète sur la façade maritime. L’étude comparative de plusieurs zones du bassin de la Seine met en évidence les variabilités temporelles et spatiales et interroge la validité des faciès régionaux (Augereau et al., 2007). L''existence d'un « faciès Marne » , proposé à l’issue de synthèses sur les pratiques funéraires, le mobilier en matière dure animale et la parure, est à nouveau validée par l''industrie lithique.

Research on damage and identification of mortise-tenon joints stiffness in ancient wooden buildings based on shaking table test

Based on the shaking table tests of a 1:3.52 scale one-bay and one-story ancient wooden structure, a simplified structural mechanics model was established, and the structural state equation and observation equation were deduced. Under the action of seismic waves, the damage rule of initial stiffness and yield stiffness of the joint was obtained. The force hammer percussion test and finite element calculations were carried out, and the structural response was obtained. Considering the 5% noise disturbance in the laboratory environment, the stiffness parameters of the mortise-tenon joint were identified by the partial least squares of singular value decomposition (PLS-SVD) and the Extended Kalman filter (EKF) method. The results show that dynamic and static cohesion method, PLS-SVD, and EKF method can be used to identify the damage degree of structures, and the stiffness of the mortise-tenon joints under strong earthquakes is reduced step by step. Using the proposed model, the identified error of the initial stiffness is about 0.58%-1.28%, and the error of the yield stiffness is about 0.44%-1.21%. This method has high accuracy and good applicability for identifying the initial stiffness and yield stiffness of the joints. The identification method and research results can provide a reference for monitoring and evaluating actual engineering structures.

An analysis of intraocular metallic foreign body injury during hammer percussion

Objective: To investigate the cause of intraocular metallic foreign body injury during hammer percussion and to observe the structure of the metallic foreign bodies. Methods: A retrospective analysis was performed in 21 inpatients with metallic foreign body injury in the posterior segment from January 2013 to April 2016. The foreign bodies were removed by magnetic drawing through external route of the sclera or vitrectomy. The shape of the foreign bodies was analyzed and the structural characteristics were observed under a metallurgical microscope. The visual acuity of the patients was compared before and after treatment. Results: All patients were discharged at one week after surgery. There was no significant difference in mean best corrected visual acuity of the patients between before treatment and after treatment (1.20±0.87 vs. 1.08±0.89, t=1.516, P>0.05). The metallic foreign bodies in all the 21 cases were magnetic and the injuries in 15 cases (71.43%) were caused by hammering on hard objects. The foreign bodies were mainly lamellar and shaped like a leaf or a lance. And the lamellar martensite structure was observed under a metallurgical microscope. Conclusion: The intraocular metallic foreign body injury often occurs during hammer percussion and the microstructure of the foreign bodies is lamellar martensite structure.

Contraction response to muscle percussion: A reappraisal of the mechanism of this bedside test

ObjectiveTo study whether the contraction evoked by muscle percussion stems from the excitation of the muscle or of the nerve and to discuss the changes of this response in neuromuscular disorders. MethodsIn 30 neurologically healthy patients undergoing surgery (for ear, nose, or throat problems unrelated to the study) under general anesthesia with propofol and sufentanil we measured with an electrogoniometer the maximal dorsiflexion of the ankle evoked by reflex hammer percussion of the tibialis anterior muscle before and under neuromuscular junction blockade with rocuronium bromide. In 3 additional healthy volunteers we searched for F-waves to disclose whether percussion excites axons within the muscle. ResultsResponses from 28 neurologically healthy patients (15 women) were analyzed after exclusion of 2 due to technical problems. Mean age (SD) was 28 (9) years. Maximal dorsiflexion of the ankle was not significantly modified by neuromuscular junction blockade (mean difference 0.01 mV [95%CI, −0.07 to 0.08], p=0.879). Muscle percussion evoked F-waves in the 3 healthy volunteers tested. ConclusionsMaximal contraction response to muscle percussion has a muscular rather than a neural origin. However, percussion also excites axons within the muscle. SignificanceThese findings may provide clues to understand the changes observed in neuromuscular disorders.

The lithic assemblages of Donggutuo, Nihewan basin: Knapping skills of early pleistocene hominins in North China.

Donggutuo (DGT) is one of the richest archaeological localities in the Nihewan Basin of North China, thereby providing key information about the technological behaviours of early hominins in eastern Asia. Although DGT has been subject of multiple excavations and technological studies over the past several decades, few detailed studies on the lithic assemblages have been published. Here we summarize and describe the DGT lithic assemblages, examining stone tool reduction methods and technological skills. DGT dates to ca. 1.1 Ma, close to the onset of the mid-Pleistocene climate transition (MPT), indicating that occupations at DGT coincided with increased environmental instability. During this time interval, the DGT knappers began to apply innovative flaking methods, using free hand hard hammer percussion (FHHP) to manufacture pre-determined core shapes, small flakes and finely retouched tools, while occasionally using the bipolar technique, in contrast to the earlier and nearby Nihewan site of Xiaochangliang (XCL). Evidence for some degree of planning and predetermination in lithic reduction at DGT parallels technological developments in African Oldowan sites, suggesting that innovations in early industries may be situational, sometimes corresponding with adaptations to changes in environments and local conditions.