Degree Of Size Reduction Research Articles

A comparison of ore pre-concentration efficiency between two high voltage pulse generator systems

High Voltage Pulse (HVP) enabled ore pre-concentration can potentially provide large energy savings and the ability to upgrade low-grade ores for the mining industry. Two types of pulse generator systems commonly used in HVP breakage are Marx generators and pulse transformers. This initial assessment compares the pre-concentration performance of a SelFrag Lab Unit (utilising a Marx generator) and a custom-built HVP machine (employing a pulse transformer) from Huazhong University of Science and Technology (HUST). Eight sets of experimental results using the two generator systems were collected. Two approaches were taken to analyse the data; a trendline approach using all eight sets of data, and a single-point comparison approach with matched specific energy inputs. The results show that there are significant differences in pre-concentration efficiencies with the HUST machine performing better. To elucidate the potential causes, the degree of size reduction (t10), breakage probability, and selective breakage were investigated for the two generator systems. It is likely that the efficiency of selective breakage is one of the major causes, with the HUST machine presenting better results at selectively breaking high-grade particles and consuming less energy. Additionally, the two generator systems have different energy per discharge levels; the effect of this difference should be investigated in future work.

Abstract CT019: A phase I trial of the combination of the dual RAF-MEK inhibitor VS-6766 and the FAK inhibitor defactinib: Evaluation of efficacy in KRAS mutated NSCLC

Abstract Background KRAS is a known oncogenic driver in non-small cell lung cancer (NSCLC), with KRAS G12C and G12V mutations occurring in ~13% and ~7% of the of NSCLC ( adenocarcinoma subtype). The dual RAF-MEK inhibitor VS-6766 has shown single agent activity against G12V KRAS mutated NSCLC (Guo C et al Lancet Oncology 2020, 21:1478-88). Based on pre-clinical data, we hypothesised that augmented focal adhesion kinase (FAK) signalling is a mechanism of resistance to MEK inhibition and devised the current clinical trial. We have previously reported the safety of an intermittent schedule of the combination of VS-6766 and the FAK inhibitor defactinib and its efficacy in low grade serous ovarian cancer (Shinde et al., AACR 2020). We now report the activity of the combination in KRAS mutated NSCLC. Methods Patients were treated with an intermittent dose of drugs VS-6766 at 3.2 - 4 mg twice a week and defactinib 200 mg twice daily in the dose escalation and expansion cohorts of the study. Both drugs were administered three weeks on/one week off in 28-day cycles. We aim to recruit 20 patients with KRAS mutated NSCLC in an expansion cohort. Results To date, 19 patients with KRAS mutated NSCLC have been treated in the dose escalation and expansion cohorts. All patients had been previously treatment with a PD-1 or PDL-1 targeting immune checkpoint inhibitor. The median age was 64 years (22 - 73), M/F ratio was 7/12, and the median prior lines of treatment was 3. Currently, 17 of 19 patients have had at least one re-staging assessment, 2/17 (12%) patients had a partial response and 10/17 (59%) had stable disease as their best response. Of note, 11/17 (65%) patients had a degree of reduction in size of their tumours and 5/17 (29%) have been treated for 6 months or more with 3 patients still on treatment. Interestingly, 2/2 (100%) of the KRAS G12V NSCLC patients showed a partial response. Conclusions Developing new treatments for non-G12C KRAS mutated NSCLC is an area of unmet need. The combination of VS-6766 and defactinib treatment in cohorts of patients with NSCLC pre-treated with chemotherapy and immunotherapy has shown anti-tumour activity in subsets of patients with KRAS mutated NSCLC, in particular those with tumours harbouring KRAS G12V mutations. A registration-directed study evaluating VS-6766 ± defactinib for treatment of recurrent NSCLC with KRAS G12V mutation (NCT04620330) has been initiated Citation Format: Matthew G. Krebs, Rajiv Shinde, Rozana Abdul Rahman, Rafael Grochot, Martin Little, Jenny King, Joseph Kitchin, Mona Parmar, Alison Turner, Muneeb Mahmud, Christina Yap, Nina Tunariu, Juanita Lopez, Johann S. De Bono, Udai Banerji, Anna Minchom. A phase I trial of the combination of the dual RAF-MEK inhibitor VS-6766 and the FAK inhibitor defactinib: Evaluation of efficacy in KRAS mutated NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT019.

Role of particle fineness on engineering properties and microstructure of fly ash derived geopolymer

Fly ash is ball milled for 30 and 90 min duration to obtain two finer fractions. The degree of size reduction is very significant at the early stage of milling, then because of agglomeration effect size reduction becomes sluggish. The effect of particle size on physical, mechanical and microstructural properties of resultant geopolymer is elucidated. The physical properties and mechanical strength improvement with milling time is attributed with formation of higher amount of alkaline alumino-silicate (N-A-S-H) hydrated gel. The weight loss profile in Thermo-gravimetric analysis (TGA) indicates more hydrated gel formation and lower carbonation with finer fraction. Different techniques such as Fourier transforms infrared spectroscopy (FTIR), X-ray diffractometer (XRD), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) have been used for microstructural evaluation of geopolymers. In FTIR, the asymmetric stretching of Si–O–T (T is Si/Al) has been shifted towards lower frequency due to structural alteration of Al–Si network. The crystalline peak intensity has been decreased because of formation of amorphous gel after geopolymerization, detected by XRD. Under SEM and TEM, finer fraction is characterized with formation of more reaction product. The counts of un-reacted and non-bridge particles are decreased with size reduction.

T2 prolongation in the cerebellar vermis on prenatal MRI of fetuses with Chiari 2 malformations

To describe a new finding in fetuses with Chiari 2 malformations recognised at in utero (iu) magnetic resonance imaging (MRI), specifically T2 prolongation (high signal) in the cerebellar vermis. This was a prospective observational study of iuMRI studies performed at two time points on 20 fetuses with Chiari 2 malformations and 10 control fetuses at the same time points. High T2 signal in the cerebellar vermis was noted and correlated with posterior fossa dimensions was assessed. High T2 signal in the cerebellar vermis was found in over half of the fetuses with a Chiari 2 malformation, but was not correlated with the degree of reduction in size of the bony posterior fossa. The present findings suggest that abnormal high T2 signal in the cerebellum is common in fetuses with Chiari 2 malformations and although the cause of the signal change is not known at present it may represent vasogenic oedema as a result of restricted venous drainage.

ОСОБЕННОСТИ ЛАБОРАТОРНЫХ ЯМР-ИССЛЕДОВАНИЙ БУРОВОГО ШЛАМА

NMR studies of core samples of different disintegration degrees were carried out to determine their reservoir properties depending on the degree of size reduction. It was established that the results do not depend on the particle size of the measured sample and are consistent with the results of standard petrophysical studies performed on core samples. It is shown that the data operatively obtained on the drill cuttings by the NMR method can be used as initial information in interpreting production well logging before conducting detailed petrophysical core studies. The results of studying drill cuttings allow to obtain reservoir properties of productive layers even at intervals without core sampling.

Downsizing feature of microphase-separated structures via intramolecular crosslinking of block copolymers.

A novel strategy for downsizing the feature of microphase-separated structures was developed via the intramolecular crosslinking reaction of block copolymers (BCPs) without changing the molecular weight. A series of BCPs consisting of poly[styrene-st-(p-3-butenyl styrene)] and poly(rac-lactide) (SBS-LA) was subjected to Ru-catalyzed olefin metathesis under highly diluted conditions to produce intramolecularly crosslinked BCPs (SBS(cl)-LAs). Small-angle X-ray scattering measurement and transmission electron microscopy observation of the SBS(cl)-LAs revealed feature size reduction in lamellar (LAM) and hexagonally close-packed cylinder (HEX) structures in the bulk state, which was surely due to the restricted chain dimensions of the intramolecularly crosslinked SBS block. Notably, the degree of size reduction was controllable by varying the crosslink density, with a maximum decrease of 22% in the LAM spacing. In addition, we successfully observed the downsizing of the HEX structure in the thin film state using atomic force microscopy, indicating the applicability of the present methodology to next-generation lithography technology.

Evaluation of HPGR and VRM for dry comminution of mineral ores

The mining industry is searching for more energy efficient and dry comminution equipment as an alternative to conventional crushing followed by wet grinding circuits. This is a result of growing challenges associated with the increasing energy cost, scarcity of water resources and stricter environmental legislation. Dry comminution technologies, such as High Pressure Grinding Rolls (HPGR) and Vertical Roller Mills (VRM), have been successfully used in other industries such as cement and coal for decades, and the literature claims that these technologies are more energy efficient than conventional comminution practices. Pilot scale testing was conducted for each of these technologies using rock with properties similar to many mineral ores to test the claims in the literature and evaluate the applicability for hard rock mining operations. Whilst the test results for the HPGR and VRM are not directly comparable (due to different degree of size reduction), both demonstrated the potential for considerable energy savings compared to conventional ball milling. The HPGR and air classification circuit used 20 - 30 % less energy than the HGPR, screen, ball mill circuit. While VRM was estimated to use 10 - 30 % less energy (depending on the type of VRM) than a ball mill circuit for a similar degree of comminution.

Salt-kneading: alternative sizing of active pharmaceutical ingredients?

The most of currently produced active pharmaceutical ingredients (APIs) are poorly soluble in the human body. One of the options how to increase their dissolution rate is reducing their particle size. If very small particles of API are desired, traditional milling methods often cause smeared, agglomerated or non-flowing particles due to the forces applied. We tried to compare some of milling methods with the salt-kneading method, which is not typically used in the pharmaceutical industry. Salt-kneading process is driven by several variable parameters (e.g. the amount, hardness and particle size of the salt-kneading material), which influence the degree of size reduction of API particles which are chafed by a surplus of salt-kneading material. A model poorly-soluble API was separately processed with oscillation mill, vibratory mill and kneader; and the morphology, size distribution and solid form of prepared particles were analyzed. Our basic variation of salt-kneading parameters showed the potential of the salt-kneading method, which appears a very effective method of API controlled reduction. The final size can be modified according to the amount and properties of the salt-kneading material. The availability of such a method equips pharmaceutical scientists with a size-reduction method that provides very small, rounded and free-flowing particles of the poorly soluble API and reduces non-preferred needle shape.

Soft and Hard Tissue Changes around Tissue-Oriented Tulip-Design Implant Abutments: A 1-Year Randomized Prospective Clinical Trial.

The advantages of platform switching using narrower abutments remain controversial. Many researchers suggest that platform switching can yield enhanced clinical results, while others remain skeptical. We hypothesize that the effectiveness of platform switching might be associated with the degree of reduction in size of the abutment. To radiographically and clinically examine a new abutment design created to move the implant-abutment interface farther medially. This was a prospective, randomized controlled clinical trial that included 27 patients (41 MIS Lance Plus® implants; MIS Implant Technologies, Karmiel, Israel). The patients' age ranged from 39 to 75 years. At the second stage of the surgery, the implants were randomly assigned to either the new platform switch Tulip abutment (TA) design or to the standard platform abutment (SA). Implant probing depth (IPD) and bleeding on probing (BOP) were recorded at baseline and after 12 months. Standardized periapical radiographs were taken (at baseline and at 12 months) and the marginal bone height measured. All implants were successfully integrated. The mean IPD at 1 year post-op was 2.91 mm for the SA group and 2.69 mm for the TA group (p > .05). Similarly, the BOP at 1 year was almost identical in both groups. The mean values of bone resorption at baseline were 0.98 ± 0.37 mm and 0.69 ± 0.20 for the TA and SA groups, respectively (p > .05). Bone loss (baseline to 12 months) was significantly greater in the SA group compared with the TA group. Use of the new TA, with its significantly downsized diameter, resulted in reduced bone loss at 1 year. Further research will be required to assess the long-term effect of this abutment on peri-implant health.

Parametric Evaluation of Coal Comminution by Waterjets

In this study, comminution of coal with waterjets was performed to determine the factors that influence the particle size reduction. To carry out these experiments, a bituminous coal sample with an ash value of 31% was exposed to waterjet action within a conventional abrasive cutting head coupled with a specially designed cavitation chamber. Original coal feed of 371 µm volume mean diameter and its subsamples of 59, 172, 323, and 527 µm were used to investigate the effect of pressure on particle size reduction. For the purpose of this study, the comminution system was operated at 69, 138, 207, and 276 MPa. Physical properties such as particle size distribution and volume mean diameter were used for evaluation of the efficiency of comminution. Initial feed size was found as a dominant factor affecting the degree of size reduction. The increase in the cavitation system operating pressure resulted in finer products. Scanning electron microscopy studies of particle shape and morphology indicated transition from flaky to round and blocky particle shapes as a result of pressure increase. Severe clay dispersion was associated with all test conditions.

Effects of operating parameters on the efficiency of dry stirred milling

Stirred media milling is an industrially accepted efficient grinding method for fine and coarse particles. The stirred mills can be operated both in vertical and horizontal configurations and the selection depending on the process variables. Successful operation of horizontal stirred milling (i.e. IsaMill) in wet applications encouraged the studies in dry applications. In this study, series of dry grinding tests were performed in a prototype horizontal stirred mill (42L) to investigate the effects of operating parameters such as stirrer speed, feed rate, media filling and ball size on grinding considering the degree of size reduction and the energy consumption. The test results have shown that the stirrer speed, the media size and the media filling are directly proportional and the feed rate is inversely proportional with the specific energy consumption. Besides, energy savings up to 27% were achieved by adjusting the milling conditions properly (suitable media size) and the size reduction values (F50/P50) were between 1.05 and 2.42.

Morphological and population responses to deer grazing for herbaceous species in Nara Park, western Japan

AbstractTo quantify the morphological and population responses of plants to grazing by deer, we conducted two deer‐exclusion experiments in Nara Park, western Japan. The first experiment assessed the morphological differences in 10 traits of two species with erect growth (Oxalis corymbosa and Cyperus brevifolius. var. leiolepis) and two species with prostrate growth (Oxalis corniculata and Hydrocotyle maritima) between shoots inside and outside of the exclosures at the end of a growing season (late autumn). The size and weight of the leaves, stems and reproductive organs of the four perennials were significantly smaller outside the exclosures. The degree of size reduction was highest for an erect species, O. corymbosa, compared with the other three species, and was similar between the two prostrate species. The second experiment, using 11 erect species and 15 prostrate species, demonstrated that erect species exhibited greater reduction in leaf length and cover in the grazing environments compared with prostrate species, suggesting that the erect species suffered more from grazing. In conclusion, many of the plant species reduced their size under grazing pressure during the growing season, but the nature of the changes depended on the growth form of each species. It remains unclear whether the morphological reduction was an adaptive response to grazing.

ORIGINAL ARTICLE: Mammals of Borneo – small size on a large island

AbstractAim Island mammals have featured prominently in models of the evolution of body size. Most of these models examine size evolution across a wide range of islands in order to test which island characteristics influence evolutionary pathways. Here, we examine the mammalian fauna of a single island, Borneo, where previous work has detected that some mammal species have evolved a relatively small size. We test whether Borneo is characterized by smaller mammals than adjacent areas, and examine possible causes for the different trajectories of size evolution between different Bornean species.Location Sundaland: Borneo, Sumatra, Java and the Malay/Thai Peninsula.Methods We compared the mammalian body size frequency distributions in the four areas to examine whether the large mammal fauna of Borneo is more depauperate than elsewhere. We measured specimens belonging to 54 mammal species that are shared between Borneo and any of the other areas in order to determine whether there is an intraspecific tendency for Bornean mammals to evolve small body size. Using data on diet, body size and geographical ranges we examine factors that are thought to influence body size.Results Borneo has fewer large mammals than the other areas, but this is not statistically significant. Large Bornean mammals are significantly smaller than their conspecifics in the other regions, while there are no differences between the body sizes of mammals on Sumatra, Java and the Malay/Thai Peninsula. The finding that large mammals show the greatest size difference between Borneo and elsewhere contrasts with some models of size evolution on islands of different areas. Diet does not correlate with the degree of size reduction. Sunda region endemics show a weaker tendency to be small on Borneo than do widespread species.Main conclusions We suggest that soil quality may drive size evolution by affecting primary productivity. On Borneo, where soils are generally poor in nutrients, this may both limit biomass and cause mammals to be reduced in body size. We hypothesize that widespread species respond to low resource abundance by reducing in size, while endemic elements of the fauna have had longer to adjust to local conditions by altering their behaviour, physiology and/or ecology, and are thus similar in size across the region.

Modeling of particle size distribution of sonicated coconut milk emulsion: Effect of emulsifiers and sonication time

Abstract Coconut milk was extracted from grated coconut meat with addition of water by a hydraulic press. This milk was mixed with emulsifiers (Gum Acacia and maltodextrin) at different ratios of emulsifier to fat (4, 2.75, and 1.5) and different maltodextrin (MD) to Gum Acacia (GA) ratio (0.67, 1.085, and 1.5). The emulsion was sonicated for different time durations (0.5–3.0 min). Particle size analysis of the sonicated coconut milk emulsion revealed that the number fraction of fat globules below 2 × 10 −6 m increased as the emulsifier to fat ratio increased. However, at the highest ratio of emulsifier to fat this trend reversed even at higher sonication times. Similar slump in the increasing trend of globules below 2 × 10 −6 m were observed at the highest value of ratio of MD to GA (1.5) studied. Modeling of particle size distribution by Rosin–Rambler–Sperling–Bennet relation was found to be a good tool for prediction of uniformity of distribution n and statistical average globule diameter M . The n values varied between 0.981 and 1.318 where as M values lied between 2.11 × 10 −6 and 4.12 × 10 −6 m. Linear regression fitting of n and M values as function of ratio of emulsifier to fat, ratio of MD to GA and the sonication time resulted in a good fit with relative deviation of 3.96% and 10.77%, respectively. These linear regression equations provided a suitable model to predict the sonication time required to achieve certain degree of size reduction with a relative deviation of 2.33%.

Morphological consequences of range fragmentation and population decline on the endangered Iberian lynx (Lynx pardinus)

AbstractThe Iberian lynx Lynx pardinus is one of the world's most endangered felids and is vulnerable to human‐induced mortality and habitat loss, which reduce population size and accelerate the loss of genetic variation. Twenty‐five metric traits of Iberian lynx skulls have been measured on 95 skulls collected between 1872 and 2003. The skulls belong to three geographically distinct areas/populations, which have recently diverged from each other as a consequence of increased habitat fragmentation: Doñana area, Sierra Morena mountains and Montes de Toledo area. The morphometric study was undertaken using univariate, multivariate and admixture analysis approaches, and all three techniques provided evidence for morphometric differentiation, both in skull size and shape, among the three populations for both males and females. Environmental and genetic forces that may have shaped these patterns are discussed. The males of the population of the Doñana area showed a different degree of reduction in size in nine of the skull traits with time, which has been suggested to be partly because of worsened habitat conditions. However, the heterogeneity of the degree of mean size reduction and the relatively high degree of reduction of some of the skull traits investigated (>4%), which have altered the original proportions between the skull variables, could also partly be attributed to inbreeding depression in the Doñana population. The phenotypic variability of the skull traits showed significant increases (two traits) or decreases (nine traits) with time, and this different pattern of change with time has been suggested to be because of a different number of genes controlling the traits with different degrees of dominance and epistatic interactions. The increased phenotypic variability of two of the traits has also been attributed to a possible decreased level of developmental stability, which can be produced by environmental and/or genetic stress. The findings of this investigation contribute to the discussion about the utility and the limits of quantitative genetics techniques for conservation purposes.

A morphometric analysis of the Japanese macaque (Macaca fuscata) mandibular cheek teeth from the Torihama Shell-midden, Early Jomon Period, Fukui Prefecture, Japan

We quantitatively examined the differences in the size and proportion of the Japanese macaque (Macaca fuscata) by comparing the Early Jomon specimens from Torihama shell-midden, Fukui Prefecture and modern specimens from Fukui Prefecture. The purpose of this study was to explore the temporal change in the proportion and size of teeth of the Japanese macaques based on the quantified data. The result of measurements of lower premolars and molars demonstrated that sexual dimorphism was evident only among the modern specimens where the females were significantly smaller than males. The size of male Torihama specimens was within the range of the modern population, whereas the size of the female Torihama specimens was significantly larger than the modern female population. The proportional pattern of premolars and molars for male and female Torihama specimens also differed. The results may suggest a possible difference in the degree of size reduction between males and females since the last glacial period.

Engrailed-ZmOCL1 fusions cause a transient reduction of kernel size in maize

ZmOCL1 is the founding member of the ZmOCL (Outer Cell Layer) family encoding putative transcription factors of the HD-ZIP IV class. It is expressed in the L1 cell layer of the embryo and several other tissues of maize. After determination of the intron/exon structure a mutator insertion was isolated in the upstream region. No notable phenotypes and wildtype levels of ZmOCL1 transcript were observed in homozygous mutant plants. In contrast transgenic plants carrying a fusion of the repressor domain of the Drosophila Engrailed gene with the DNA binding and dimerisation domains of ZmOCL1 showed a transient reduction of embryo, endosperm and kernel size that was most obvious around 15 DAP. An inverse relationship was observed between the degree of size reduction and the expression level of the transcript. In reciprocal crosses the size reduction was only observed when the transgenic plants were used as females and no expression of male transmitted transgenes was detected. Smaller kernels resembled younger kernels of wild-type siblings indicating that interference with ZmOCL1 function leads to an overall slow-down of early kernel development. Based on marker gene analysis ZmOCL1 may act via a modification of gibberellin levels. Phylogenetic analyses based on the intron/exon structure and sequence similarities of ZmOCL1 and other HD-ZIP IV proteins from maize, rice and Arabidopsis helped to identify orthologues and suggested an evolution in the function of individual genes after the divergence of monocots and dicots.

Influence of particle size and shape on the comminution of single particles in a rigidly mounted roll mill

In single-particle roll mill comminution, the degree of size reduction is controlled by the ratio of the nip size of the particle and the roll gap. However, the nip size or effective particle size of irregularly shaped particles is generally unknown. An experimental procedure is presented to assess nip size of irregularly shaped particles and to evaluate energy consumption and energy utilization in their comminution. A series of experiments in which the roll gap was successively reduced reveals that the height of a particle, that is, the particle's dimension normal to the plane in which it resides in its most stable position, is a satisfactory approximation of the nip size which can be conveniently measured with a slot classifier. The nip size or particle height is distributed in √2 and √4 sieve–size fraction according to a Gaussian normal distribution, the median size being roughly 80% of the geometric sieve size. The energy investment for comminuting single particles in a rigidly mounted roll mill varies with the nip size in the manner of a power function. Estimated Weibull coefficients of uniformity for dolomite, galena, and quartz are 7.5, 1.9, and 7.9. Product size distributions of comminuted nip-size fractions are self-preserving in a dimensionless size X/ X 50 and thus, the median size is a measure of product fineness. Grindabilities calculated from the linear reduction ratio energy relationships are 7.8, 14.0, and 4.5 t/kWh for dolomite, galena, and quartz, respectively. Single-particle grindabilities of these three minerals are power functions of the nip size. Dolomite and quartz data follow closely Rittinger's Law of Comminution.

Long-term follow-up of residual mediastinal masses in treated Hodgkin's disease using MR imaging.

Long-term follow-up of residual mediastinal masses in treated Hodgkin's disease using MR imaging. Ten patients, with substantial residual mediastinal masses of low signal intensity (SI) in the T2-weighted image (T2WI), were reinvestigated with MR 19-79 months after completing treatment of Hodgkin's disease. All patients were in complete remission. During the follow-up period, the masses had decreased in size by 0-95% (median 67%) as compared to their initial post-therapy size. The SI continued to be low in the T2WI and was unaffected by the degree of size reduction. It is speculated that these mainly fibrotic residual masses undergo slow degradation of the fibrotic part and/or resorption of remaining inflammatory tissue. It is important to understand the natural, long-term MR imaging changes of these residual masses in order more easily to recognize tumour recurrence or other pathologic conditions.

Lack of segmental selectivity in elimination of synapses from soleus muscle of new-born rats.

The elimination of polyneuronal innervation from neonatal rat soleus muscle was studied by comparing the extent of synapse loss by motor neurones emerging through each of the two spinal nerves (L4 and L5) supplying the muscle. The fraction of muscle fibres receiving innervation from the L4 spinal nerve declined from an average of 75% in 6-day-old animals (when all fibres are polyneuronally innervated) to 18% in animals older than 16 days (when almost all muscle fibres are singly innervated). By comparison innervation by the L5 spinal nerve declined from 99% of the fibres at 6 days to 83% of the fibres after 16 days. As a result of synapse elimination there is a greater reduction in the innervation of the muscle by the L4 nerve. The difference in loss of muscle fibres innervated by L4 vs. L5 was not, however, due to a greater degree of synapse elimination of L4 motor nerve terminals. As shown by measurements of the sizes of motor units, both L4 and L5 have units which on average are about four to five times larger at 6 days than at the conclusion of synapse elimination. Thus L4 and L5 motor neurones undergo approximately the same degree of size reduction. The apparently disproportionate loss of muscle innervation by the L4 nerve is explained by the fact that L4 usually contains only a small portion of the total of soleus motor neurones. I therefore conclude that there is no selective loss of synapses based on spinal origin of motor neurones.