Large Increase In Volume Research Articles

Stable Li-ion battery anodes by in-situ polymerization of conducting hydrogel to conformally coat silicon nanoparticles

Silicon has a high-specific capacity as an anode material for Li-ion batteries, and much research has been focused on overcoming the poor cycling stability issue associated with its large volume changes during charging and discharging processes, mostly through nanostructured material design. Here we report incorporation of a conducting polymer hydrogel into Si-based anodes: the hydrogel is polymerized in-situ, resulting in a well-connected three-dimensional network structure consisting of Si nanoparticles conformally coated by the conducting polymer. Such a hierarchical hydrogel framework combines multiple advantageous features, including a continuous electrically conductive polyaniline network, binding with the Si surface through either the crosslinker hydrogen bonding with phytic acid or electrostatic interaction with the positively charged polymer, and porous space for volume expansion of Si particles. With this anode, we demonstrate a cycle life of 5,000 cycles with over 90% capacity retention at current density of 6.0 A g(-1).

Failure behavior of rubber O-ring under cyclic exposure to high-pressure hydrogen gas

This paper presents the effects of hydrogen pressure, ambient temperature and pressure cycle pattern on fracture behavior of O-rings moulded from a peroxide-crosslinked EPDM rubber with white reinforcing filler under cyclic exposure to high-pressure hydrogen gas. By using a developed durability tester which enables the O-rings to expose cyclically high-pressure hydrogen gas, pressure cycle tests were performed at hydrogen pressures ranging from 10 to 70MPa and ambient temperatures ranging from 30 to 100°C under two pressure cycle patterns (test frequencies). The cyclic hydrogen exposure caused cracks in the O-rings, and their crack damage became more serious with an increase in the hydrogen pressure and the ambient temperature. The serious crack damage under high temperature is believed to be due to degradation of mechanical properties with increasing ambient temperature. At a hydrogen pressure of 10MPa, cracks (blisters) caused by bubbles formed from supersaturated hydrogen molecules after decompression were observed. At a hydrogen pressure of 35MPa or more, a large volume increase of the O-rings was observed by swelling; then, its volume increase induced extrusion fracture of the O-rings in addition to blister fracture. The crack damage also became more serious with a decrease in test frequency. The effect of the test frequency on the crack damage of the O-rings is presumed to be attributed to time-dependent crack growth behavior of the EPDM rubber.

Lung/chest expansion contributes to generation of pleasantness associated with dyspnoea relief

Pleasantness associated with dyspnoea relief or ‘respiratory pleasure’ is considered as a particular sensory experience. The purpose of this study is to elucidate the mechanism of generation of this particular sensory experience. After taking deep breaths during normal breathing, 35 healthy subjects received three different magnitudes of inspiratory loads (light: 8.4; moderate: 23.4; severe: 70.5cmH2O/L/s) to induce dyspnoeic sensation. We found that (1) deep breaths during normal breathing rarely induce ‘respiratory pleasure’, (2) a sudden removal of dyspnoea alone is not sufficient to produce ‘respiratory pleasure’, and (3) the generation of ‘respiratory pleasure’ can be observed when a sudden removal of dyspnoea accompanies a large increase in tidal volume (VT). In addition, qualitative assessment of ‘respiratory pleasure’ showed that this sensation is compatible with a strong, positively valenced sensation. These findings indicate that an increase in VT after removal of respiratory loading plays a crucial role in generation of ‘respiratory pleasure’ that is a specific sensory-emotional experience.

Brain Growth of the Domestic Pig (Sus scrofa) from 2 to 24 Weeks of Age: A Longitudinal MRI Study

An animal model with brain growth similar to humans, that can be used in MRI studies to investigate brain development, would be valuable. Our laboratory has developed and validated MRI methods for regional brain volume quantification in the neonatal piglet. The aim of this study was to utilize the MRI-based volume quantification technique in a longitudinal study to determine brain growth in domestic pigs from 2 to 24 weeks of age. MRI data were acquired from pigs 2–24 weeks of age using a 3-dimensional magnetization-prepared gradient echo sequence on a Magnetom Trio 3-tesla imager. Manual segmentation was performed for volume estimates of total brain, cortical, diencephalon, brainstem, cerebellar and hippocampal regions. Logistic modeling procedures were used to characterize brain growth. Total brain volume increased 130% (±12%) and 121% (±7%) from 2 to 24 weeks in males and females, respectively. The maximum increase in total brain volume occurred about the age of 4 weeks and 95% of whole brain growth occurred by the age of 21–23 weeks. Logistical modeling suggests there are sexually dimorphic effects on brain growth. For example, in females, the cortex was smaller (p = 0.04). Furthermore, the maximum growth of the hippocampus occurred about 5 weeks earlier in females than males, and the window for hippocampal growth was significantly shorter in females than males (p = 0.02, p = 0.002 respectively). These sexual dimorphisms are similar to what is seen in humans. In addition to providing important data on brain growth for pigs, this study shows pigs can be used to obtain longitudinal MRI data. The large increase in brain volume in the postnatal period is similar to that of human neonates and suggests pigs can be used to investigate brain development.

Thermo-mechanical behavior and specific volume of highly crosslinked networks based on glycerol dimethacrylate and its derivatives

Three substituent derivatives of glycerol dimethacrylate (GDMA) i.e., acetyloxypropyl dimethacrylate (Acet-GDMA), acryloyloxy-hydroxypropyl methacrylate (GMMA), and acetyloxy-acryloyloxypropyl methacrylate (Acet-GMMA) as well as GDMA were prepared and UV-homopolymerized in the presence of 2,2-dimethoxy-2-phenyloacetophenone. The obtained homopolymers were subjected to dynamic mechanical studies and the deflections versus temperature measurements (HDT) were performed. The content of unreacted double bonds, glass transition temperatures (T g) as well as degree of inhomogeneity have been examined in all studied systems. Also, expansivity was measured in the function of temperature and the effect of a substituent group on the network properties was investigated. The results show that the hydroxyl-containing networks are characterized by much lower T g and higher degree of heterogeneity than those devoid of hydroxyls. When homopolymerized, hydroxyl-free dimethacrylates disclosed untypical deflection pattern which suggests that at higher temperatures the decrease in stiffness is compensated or even overrated by the increase in the specific volume. Expansivity measurements revealed twice as large volume increase of the acetylated polymers as opposed to their hydroxyl-containing analogs. Following these findings, a mechanism of thermally induced polymer “swelling” was proposed.

Postnatal development of the amygdala: A stereological study in macaque monkeys

Abnormal development of the amygdala has been linked to several neurodevelopmental disorders, including schizophrenia and autism. However, the postnatal development of the amygdala is not easily explored at the cellular level in humans. Here we performed a stereological analysis of the macaque monkey amygdala in order to characterize the cellular changes underlying its normal structural development in primates. The lateral, basal, and accessory basal nuclei exhibited the same developmental pattern, with a large increase in volume between birth and 3 months of age, followed by slower growth continuing beyond 1 year of age. In contrast, the medial nucleus was near adult size at birth. At birth, the volume of the central nucleus was half of the adult value; this nucleus exhibited significant growth even after 1 year of age. Neither neuronal soma size, nor neuron or astrocyte numbers changed during postnatal development. In contrast, oligodendrocyte numbers increased substantially, in parallel with an increase in amygdala volume, after 3 months of age. At birth, the paralaminar nucleus contained a large pool of immature neurons that gradually developed into mature neurons, leading to a late increase in the volume of this nucleus. Our findings revealed that distinct amygdala nuclei exhibit different developmental profiles and that the amygdala is not fully mature for some time postnatally. We identified different periods during which pathogenic factors might lead to the abnormal development of distinct amygdala circuits, which may contribute to different human neurodevelopmental disorders associated with alterations of amygdala structure and functions.

Expansion of the fetoplacental vasculature in late gestation is strain dependent in mice.

How the fetoplacental arterial tree grows and expands during late gestational development is largely unknown. In this study, we quantified changes in arterial branching in the fetal exchange region of the mouse placenta during late gestation, when capillarization increases rapidly. We studied two commonly used mouse strains, CD1 and C57Bl/6 (B6), at embryonic days (E)13.5, 15.5, and 17.5. B6 mice differ from CD1 mice by exhibiting a blunted fetal weight gain in late gestation. We found that B6 capillarization and interhemal membrane thinning were reduced and placental hypoxia-inducible factor-1α and VEGF-A expression were higher than CD1 near term. Automated vascular segmentation of microcomputed tomography data sets revealed that the number of arterial vessels ≥50 μm remained constant during late gestation in both strains, despite large increases in downstream capillary volume quantified by stereology (+65% in B6 mice and +200% in CD1 mice). Arterial diameters expanded in both strains from E13.5 to E15.5; however, diameters continued to expand to E17.5 in B6 mice only. The diameter scaling coefficient at branch sites was near optimal (−3.0) and remained constant in CD1 mice, whereas it decreased, becoming abnormal, in B6 mice at term (−3.5 ± 0.2). Based on arterial tree geometry, resistance remained constant throughout late gestation (∼0.45 mmHg·s·μl−1) in CD1 mice, whereas it decreased by 50% in late gestation in B6 mice. Quantification of the fetoplacental vasculature revealed significant strain-dependent differences in arterial and capillary expansion in late gestation. In both strains, enlargement of the fetoplacental arterial tree occurred primarily by increased arterial diameters with no change in segment numbers in late gestation.

Stable magnetostructural coupling with tunable magnetoresponsive effects in hexagonal ferromagnets

The magnetostructural coupling between the structural and the magnetic transition has a crucial role in magnetoresponsive effects in a martensitic-transition system. A combination of various magnetoresponsive effects based on this coupling may facilitate the multifunctional applications of a host material. Here we demonstrate the feasibility of obtaining a stable magnetostructural coupling over a broad temperature window from 350 to 70 K, in combination with tunable magnetoresponsive effects, in MnNiGe:Fe alloys. The alloy exhibits a magnetic-field-induced martensitic transition from paramagnetic austenite to ferromagnetic martensite. The results indicate that stable magnetostructural coupling is accessible in hexagonal phase-transition systems to attain the magnetoresponsive effects with broad tunability.

The Benefit of Enhanced Contractility in the Infarct Borderzone: A Virtual Experiment

Objectives: Contractile function in the normally perfused infarct borderzone (BZ) is depressed. However, the impact of reduced BZ contractility on left ventricular (LV) pump function is unknown. As a consequence, there have been no therapies specifically designed to improve BZ contractility. We tested the hypothesis that an improvement in borderzone contractility will improve LV pump function. Methods: From a previously reported study, magnetic resonance imaging (MRI) images with non-invasive tags were used to calculate 3D myocardial strain in five sheep 16 weeks after anteroapical myocardial infarction. Animal-specific finite element (FE) models were created using MRI data and LV pressure obtained at early diastolic filling. Analysis of borderzone function using those FE models has been previously reported. Chamber stiffness, pump function (Starling’s law) and stress in the fiber, cross fiber, and circumferential directions were calculated. Animal-specific FE models were performed for three cases: (a) impaired BZ contractility (INJURED); (b) BZ-contractility fully restored (100% BZ IMPROVEMENT); or (c) BZ-contractility partially restored (50% BZ IMPROVEMENT). Results: 100% BZ IMPROVEMENT and 50% BZ IMPROVEMENT both caused an upward shift in the Starling relationship, resulting in a large (36 and 26%) increase in stroke volume at LVPED = 20 mmHg (8.0 ml, p < 0.001). Moreover, there were a leftward shift in the end-systolic pressure volume relationship, resulting in a 7 and 5% increase in LVPES at 110 mmHg (7.7 ml, p < 0.005). It showed that even 50% BZ IMPROVEMENT was sufficient to drive much of the calculated increase in function. Conclusion: Improved borderzone contractility has a beneficial effect on LV pump function. Partial improvement of borderzone contractility was sufficient to drive much of the calculated increase in function. Therapies specifically designed to improve borderzone contractility should be developed.

Structural and magnetic study of mechanically deformed Fe rich FeAlSi ternary alloys

In this work we study systematically the influence of different Al/Si ratios on the magnetic and structural properties of mechanically disordered powder Fe75Al25−xSix, Fe70Al30−xSix and Fe60Al40−xSix alloys by means of Mössbauer spectroscopy, X-ray diffraction and magnetic measurements. In order to obtain different stages of disorder the alloys were deformed by different methods: crushing induction melted alloys and ball milling annealed (ordered) alloys using different number of balls and speed. X-ray and Mössbauer data show that mechanical deformation induces the disordered A2 structure in these alloys. The results indicate that addition of Si to binary Fe–Al alloys makes the disordering more difficult. In addition, X-ray diffraction patterns show that the normalized lattice parameter variation of the disordered alloys of each composition decreases monotonically with Si content, indicating clearly that Si addition opposes the large volume increase found in FeAl alloys with deformation. The study of the hyperfine fields indicates that there is a redistribution of non-ferrous atoms around Fe atoms with the disordering; indeed, there is an inversion of the behavior of the hyperfine field of the Fe atoms. On the other hand, the magnetic measurements indicate that addition of Si to binary Fe75Al25 and Fe70Al30 alloys opposes the magnetic behavior induced by Al in the magnetism of Fe.

Formation, characterization, and dynamics of onion-like carbon structures for electrical energy storage from nanodiamonds using reactive force fields

We simulate the experimentally observed graphitization of nanodiamonds into multi-shell onion-like carbon nanostructures, also called carbon onions, at different temperatures, using reactive force fields. The simulations include long-range Coulomb and van der Waals interactions. Our results suggest that long-range interactions play a crucial role in the phase-stability and the graphitization process. Graphitization is both enthalpically and entropically driven and can hence be controlled with temperature. The outer layers of the nanodiamond have a lower kinetic barrier toward graphitization irrespective of the size of the nanodiamond and graphitize within a few-hundred picoseconds, with a large volume increase. The inner core of the nanodiamonds displays a large size-dependent kinetic barrier, and graphitizes much more slowly with abrupt jumps in the internal energy. It eventually graphitizes by releasing pressure and expands once the outer shells have graphitized. The degree of transformation at a particular temperature is thereby determined by a delicate balance between the thermal energy, long-range interactions, and the entropic/enthalpic free energy gained by graphitization. Upon full graphitization, a multi-shell carbon nanostructure appears, with a shell-shell spacing of about ∼3.4 Å for all sizes. The shells are highly defective with predominantly five- and seven-membered rings to curve space. Larger nanodiamonds with a diameter of 4 nm can graphitize into spiral structures with a large (∼29-atom carbon ring) pore opening on the outermost shell. Such a large one-way channel is most attractive for a controlled insertion of molecules/ions such as Li ions, water, or ionic liquids, for increased electrochemical capacitor or battery electrode applications.

Aortic valve surgery: Marked increases in volume and significant decreases in mechanical valve use—an analysis of 41,227 patients over 5 years from the Society for Cardiothoracic Surgery in Great Britain and Ireland National database

Aortic valve replacement is accepted as a standard treatment for aortic stenosis and regurgitation. To help plan the national requirement for conventional and catheter-based procedures, we have analyzed the Society for Cardiothoracic Surgery in Great Britain and Ireland audit database to look at changes in practice over time. All patients undergoing conventional aortic valve replacement with or without coronary artery surgery from April 2004 to March 2009 were included. The main outcome measures were changes in the number, characteristics, operative details, and in-hospital mortality. We have looked particularly at trends and outcomes in elderly and high-risk patients (EuroSCORE of 10 or more) who may now be considered for percutaneous aortic valve insertion. A total of 41,227 patients underwent aortic valve surgery over 5 years with an in-hospital mortality of 4.1%. The annual number increased from 7396 in 2004-2005 to 9333 in 2008-2009, with significant increases (P < .0005) in mean age (68.8-70.2 years), the proportion of patients with aortic stenosis (62.4%-65.1%), octogenarians (13.6%-18.4%), high-risk patients (24.6%-27.7%), and those receiving biological valves (65.4%-77.8%). The incidence of permanent cerebrovascular accident was 1.2% and 1.0% in patients having only an aortic valve replacement. The dialysis rate was 4.5% and the reoperation rate for bleeding was 6.6%. Overall mortality decreased from 4.4% in 2004-2005 to 3.7% in 2008-2009. Survival to a mean follow-up of 2.5 years was 89%. We have seen a large increase in annual volume of aortic valve replacements, with more patients undergoing surgery for aortic stenosis and an increase in surgery in the elderly and high-risk patients.

Assessment of Fluid Responsiveness

Assessment of Fluid Responsiveness

The Association of Robotic Surgical Technology and Hospital Prostatectomy volumes

Despite limited and conflicting evidence for the efficacy of newly developed robotic technology for laparoscopic prostatectomy, this technology is spreading rapidly. Because the newer technology is more costly, reasons for this rapid adoption are unclear. The authors of this report sought to determine whether hospital acquisition of robotic technology was associated with volume of prostate cancer surgery. The inpatient dataset of claims records from 2002 to 2008 and the acquisition dates of robotic technology were used to examine the rates of prostatectomy in Wisconsin hospitals. In analyses that accounted for hospital and referral region characteristics, changes in hospital prostatectomy volume were examined for their association with technology acquisition. Overall trends in the rate of prostatectomy also were examined over the study period. In total, 10,021 prostatectomies were performed in 52 hospitals in Wisconsin's 8 health referral regions during the study period. The mean quarterly prostatectomy volume in hospitals that did not acquire the technology was 4.5 in 2002 and 3.1 in 2007/2008. In contrast, the mean quarterly prostatectomy volume in hospitals that went on to acquire robotic technology was 16.5 in 2002 and 24.8 in 2007/2008. In adjusted models, the acquisition of a robot was associated with a 114% annual increase (95% confidence interval, 62%-177% annual increase) in hospital prostatectomy volume. The average Wisconsin hospital prostatectomy volume was unchanged during 2002 through 2006 but increased by 25.6% in 2007. Robotic technology acquisition occurred rapidly in Wisconsin hospitals, and hospitals that acquired a robot had large increases in prostatectomy volume.

Calibrating the Graduated Frequencies Summary Measure: Preliminary Sensitivity Findings From the Year 2000 U.S. National Alcohol Survey Informed by Drinking Diaries, Protocol Analysis, and Beverage-Type and Context Data

Objective: Graduated Frequencies (GF) alcohol consumption measures efficiently summarize drinking pattern and permit volume calculations, both vital for epidemiology and policy studies. However, few studies have assessed accuracy of standard algorithms. We conducted sensitivity and simulation exercises to gain insight into potential effects of calibrating the measure to improve assessment of volume. Method: We used drinking diaries (n=99) followed by a summary GF scale to recalibrate multi-level F and Q constants associated with volume summations. A separate protocol analysis asked respondents (n=58) how many drinks they usually had within each GF range. Third, the Year 2000 National Alcohol Survey (N10) includes a novel technique for improving recall of maximum drinks/day using contextual cues, developed to correct volume/pattern estimates. Proportions of drinking in contexts where hypothetically larger pours of wine and liquor (home, parties and “street” drinking), plus beverage potency (malt liquor beer and spirits), were used to estimate impacts of drink size and strength on volume and consumption distributions. Results: Diary results showed that the mean quantity of a GF quantity range is typically below that range’s midpoint. In a sensitivity result based on preliminary N10 national telephone data (n = 2,447 drinkers) this bias was largely offset by underestimation of GF mid-level frequencies, yielding little volume change (increases and decreases of less than 5%, depending on assumptions). The protocol analysis confirmed the quantity adjustment. In the N10 sample of drinkers, repeating the GF with contextual cues elicited a higher maximum in 15% drinkers; 9% had a large volume increase (+83%) but change was small (+3.5%) averaged over all drinkers. Lastly, pour-size/strength simulations in the same national data showed that such adjustments promise the greatest aggregate effect on population estimates. Various plausible assumptions yielded up to a 37% overall increase in mean volume. Conclusions: Results imply that GF algorithms are robust to typical recall distortions; conversely, size and type of a subjective “drink” (dose) produce the dominating measurement biases sufficient to account for much of the “dark matter”, the amount undercovered by standard self-report survey measures. Improving survey measurement is critical for making sound, evidence-based policy recommendations.

A new method to study changes in microvascular blood volume in muscle and adipose tissue: real-time imaging in humans and rat

We employed and evaluated a new application of contrast-enhanced ultrasound for real-time imaging of changes in microvascular blood volume (MBV) in tissues in females, males, and rat. Continuous real-time imaging was performed using contrast-enhanced ultrasound to quantify infused gas-filled microbubbles in the microcirculation. It was necessary to infuse microbubbles for a minimum of 5-7 min to obtain steady-state bubble concentration, a prerequisite for making comparisons between different physiological states. Insulin clamped at a submaximal concentration (∼75 μU/ml) increased MBV by 27 and 39% in females and males, respectively, and by 30% in female subcutaneous adipose tissue. There was no difference in the ability of insulin to increase muscle MBV in females and males, and microvascular perfusion rate was not increased significantly by insulin. However, perfusion rate of the microvascular space was higher in females compared with males. In rats, insulin clamped at a maximal concentration increased muscle MBV by 60%. Large increases in microvascular volume and perfusion rate were detected during electrical stimulation of muscle in rats and immediately after exercise in humans. We have demonstrated that real-time imaging of changes in MBV is possible in human and rat muscle and in subcutaneous adipose tissue and that the method is sensitive enough to pick up relatively small changes in MBV when performed with due consideration of steady-state microbubble concentration. Because of real-time imaging, the method has wide applications for determining MBV in different organs during various physiological or pathophysiological conditions.

Homogeneous deformation of metallic glass at room temperature reveals large dilatation

► We study compressive loading of a metallic glass below the yield stress. ► The directly measured density decrease verifies earlier indirect inferences. ► There is a dilatation of roughly one atomic volume per atom involved in shear. ► Volume changes cannot now be attributed only to shear bands. ► The relative changes of shear and bulk moduli are not as expected. Room-temperature uniaxial compression of Zr 46.75 Ti 8.25 Cu 7.5 Ni 10 Be 27.5 bulk metallic glass at 80% of the yield stress leads to homogeneous viscous flow. The flow in this apparently elastic regime reveals large increases in volume associated with local shearing events in the glass. The extent of this dilatation is masked in more usual tests by significant relaxation of the glass structure during and after shear. The dilatation in deformed metallic glasses can no longer be attributed only to free-volume generation at shear bands.

Negative thermal expansion emerging upon structural phase transition in ZrV2O7 and HfV2O7

ZrV(2)O(7) and HfV(2)O(7), which show negative thermal expansion (NTE) in the high-temperature phase, were investigated using X-ray diffraction and heat capacity calorimetry. Two sharp anomalies due to successive phase transitions were observed in the temperature dependence of heat capacity at 345.5 K and 373.4 K for ZrV(2)O(7) and 341.8 K and 370.3 K for HfV(2)O(7). The smallness of their combined entropies of transition suggested that the phase transitions are of displacive type. Effective phonon densities of states (DOS) described by a simple model, and mode-Grüneisen parameters of the low-temperature phase were obtained through the spectrum analyses of heat capacities of ZrV(2)O(7) and HfV(2)O(7). Their effective phonon DOS's show the three features common to NTE compounds: low-energy phonon mode, high-energy phonon mode, and a wide phonon gap in between. The mode-Grüneisen parameter of low-energy modes corresponding to translational and librational vibrations of the constituent polyhedra is negative but with a small absolute value due to the distortion of V(2)O(7) group in the low-temperature phase, resulting in positive thermal expansion. It is revealed that the release of the structural distortion upon the successive phase transitions with large volume increase leads to the NTE of ZrV(2)O(7) and HfV(2)O(7) in the high-temperature phase.

Drosophila vitelline membrane assembly: A critical role for an evolutionarily conserved cysteine in the “VM domain” of sV23

The vitelline membrane (VM), the oocyte proximal layer of the Drosophila eggshell, contains four major proteins (VMPs) that possess a highly conserved “VM domain” which includes three precisely spaced, evolutionarily conserved, cysteines (CX 7CX 8C). Focusing on sV23, this study showed that the three cysteines are not functionally equivalent. While substitution mutations at the first (C123S) or third (C140S) cysteines were tolerated, females with a substitution at the second position (C131S) were sterile. Fractionation studies showed that sV23 incorporates into a large disulfide linked network well after its secretion ceases, suggesting that post-depositional mechanisms are in place to restrict disulfide bond formation until late oogenesis, when the oocyte no longer experiences large volume increases. Affinity chromatography utilizing histidine tagged sV23 alleles revealed small sV23 disulfide linked complexes during the early stages of eggshell formation that included other VMPs, namely sV17 and Vml. The early presence but late loss of these associations in an sV23 double cysteine mutant suggests that reorganization of disulfide bonds may underlie the regulated growth of disulfide linked networks in the vitelline membrane. Found within the context of a putative thioredoxin active site (CXXS) C131, the critical cysteine in sV23, may play an important enzymatic role in isomerizing intermolecular disulfide bonds during eggshell assembly.

Impact of South Africa's Monetary Policy on the LNS Economies

The countries in the Common Monetary Area (CMA), South Africa, Lesotho, Namibia and Swaziland, have harmonised their monetary and exchange rate policies in a quasi-monetary union since 1990. Lesotho, Namibia and Swaziland (LNS) have pegged their currencies to the South African Rand thus effectively surrendering monetary policy to the South African reserve bank. The arrangement has resulted in benefits in the form of lower prices, economy on trading costs, and a large increase in trade volume and cross-border financial transactions. However, one cost that has confronted the LNS economies in this monetary arrangement is the loss of independent monetary policy decision-making for stabilisation purposes. This study applies VAR to trace the impact of South Africa Reserve Bank°Os (SARB) monetary policy on the LNS economies. Specifically, the study examines how a change in the policy instrument of the Reserve Bank of South Africa affects money, credit and level of prices in the LNS economies and consequently assesses the capability of these economies to undertake independent monetary policy. Both the impulse response functions and the cumulated forecast errors show that the lending rates, level of prices and money supply respond instantaneously to changes in the repo rate by the South African reserve bank. Our analysis confirms that the South African repo rate is the relevant policy instrument