Wall slip and flow of concentrated hard-sphere colloidal suspensions

We present a comprehensive study of the slip and flow of concentrated colloidal suspensions using cone-plate rheometry and simultaneous confocal imaging. In the colloidal glass regime, for smooth, non-stick walls, the solid nature of the suspension causes a transition in the rheology from Herschel-Bulkley (HB) bulk flow behavior at large stress to a Bingham-like slip behavior at low stress, which is suppressed for sufficient colloid-wall attraction or colloid-scale wall roughness. Visualization shows how the slip-shear transition depends on gap size and the boundary conditions at both walls and that partial slip persist well above the yield stress. A phenomenological model, incorporating the Bingham slip law and HB bulk flow, fully accounts for the behavior. Microscopically, the Bingham law is related to a thin (sub-colloidal) lubrication layer at the wall, giving rise to a characteristic dependence of slip parameters on particle size and concentration. We relate this to the suspension's osmotic pressure and yield stress and also analyze the influence of van der Waals interaction. For the largest concentrations, we observe non-uniform flow around the yield stress, in line with recent work on bulk shear-banding of concentrated pastes. We also describe residual slip in concentrated liquid suspensions, where the vanishing yield stress causes coexistence of (weak) slip and bulk shear flow for all measured rates

Big data and predictive analytics and Malaysian micro‑, small and medium businesses

Innovative technologies such as big data and predictive analytics are facilitating a global revolution in operational management. The present study aims to investigate the extent of their adoption among micro-, small and medium enterprises. The context of choice is Malaysia—a growing economy hosting some of the relatively more technologically advanced enterprises in ASEAN union. The research plan of the present paper pursued three objectives. First, we aimed to identify the general rate of adoption of BDPA. Second, we explored the most common uses of this set of innovations in Malaysian micro-, small, and medium enterprises. Third, we strove to abstract the antecedents and consequences of BDPA in micro-, small, and large frms in the manufacturing and service sectors. We discovered that BDPA are almost never used to outsource suppliers or to optimise spending and purchasing. Conversely, the most frequent applications of BDPA are in customer relationship management and in warehouse and operations improvement. Moreover, we smaller frms are more resilient to the challenges of adopting BDPA than their smaller and larger counterparts. Thus, this paper presents a snapshot of the BDPA dissemination in the micro-, small and medium ecosystem in Malaysia in 2021, while exploring opportunities for the future development and dissemination of this set of innovations

The Determinants of Micro, Small and Medium Enterprises’ (MSMEs) Performance in Nigeria: Evidence from Business Enterprise Survey

In this paper, we provide new evidence on the determinants of business enterprise performance by combining the structure conduct performance, efficiency structure and business environment factors. In particular, we focus on the major determining factors of MSMEs performance in Nigeria. We further account for possible regional variation in MSMEs performance using a cross sectional Ordinary Least Squares (OLS) with fixed effects. The latest 2014 World Bank Enterprise Survey (WBES) data for Nigeria was used and the results obtained shows that skilled labor, capital intensity, age, size, foreign ownership, percentage of export, research & development as well as bribe payment have a positive impact on MSMEs performance. Although, bribe payment is positive, it is not significant to MSME performance. This is because bribery does not translate to outright performance, rather it is a form of illegal extortion from MSMEs by government officials in order to allow them remain in business. On the other hand, the study found degree of competition, poor electricity supply, high insecurity and difficulty in accessing finance as major setbacks to MSMEs performance in Nigeria. While we found skilled labor, age of enterprise and size to contribute significantly to MSMEs performance, contrary to some findings in the literature, we found capital intensity, foreign ownership, firm’s export, bribe payment, research & development, degree of competition, outage intensity, insecurity and difficulty in obtaining finance to be insignificant to MSMEs performance in Nigeria

The Determinants of Micro, Small and Medium Enterprises’ (MSMEs) Performance in Nigeria: Evidence from Business Enterprise Survey

In this paper, we provide new evidence on the determinants of business enterprise performance by combining the structure conduct performance, efficiency structure and business environment factors. In particular, we focus on the major determining factors of MSMEs performance in Nigeria. We further account for possible regional variation in MSMEs performance using a cross sectional Ordinary Least Squares (OLS) with fixed effects. The latest 2014 World Bank Enterprise Survey (WBES) data for Nigeria was used and the results obtained shows that skilled labor, capital intensity, age, size, foreign ownership, percentage of export, research & development as well as bribe payment have a positive impact on MSMEs performance. Although, bribe payment is positive, it is not significant to MSME performance. This is because bribery does not translate to outright performance, rather it is a form of illegal extortion from MSMEs by government officials in order to allow them remain in business. On the other hand, the study found degree of competition, poor electricity supply, high insecurity and difficulty in accessing finance as major setbacks to MSMEs performance in Nigeria. While we found skilled labor, age of enterprise and size to contribute significantly to MSMEs performance, contrary to some findings in the literature, we found capital intensity, foreign ownership, firm’s export, bribe payment, research & development, degree of competition, outage intensity, insecurity and difficulty in obtaining finance to be insignificant to MSMEs performance in Nigeria

Detection of Multidrug-Resistant Acinetobacter baumannii among Gram-Negative Bacteria Isolated from Clinical Samples

Acinetobacter baumannii is an aerobic, Gram -negative cocco-bacilli, non-fermentative, non-motile, and non-fastidious organism belonging to the genus Acinetobacter. The A. baumannii has emerged as a worldwide nosocomial pathogen causing about 80%25 of nosocomial infections comprising ventilator-acquired pneumonia, bacteremia, meningitis, urinary tract infections, skin and soft tissues infections associated with high mortality rate of approximately 63.3%25. Although literature shows sufficient information about the drug resistant A. baumannii, there has been inadequate reports on the antibiotic resistance level of this bacterium in the study area. The aim of this research was to detect Multidrug-resistant A. baumannii isolates among Gram-negative bacteria isolated from Federal Teaching Hospital, Gombe, Nigeria. A total of 1008 clinical samples were collected and cultured on MacConkey agar and Blood agar plates at 37o C for 18-24 hours. Following the incubation period, discrete colonies obtained were subjected to Gram staining. The Gram-negative isolates were identified based on conventional biochemical tests with further use of VITEK 2 COMPACT (BioMérieux, France) for confirmation of A. baumannii amongst the Gram-negative organisms. The results obtained showed that 263 Gram-negative organisms were isolated. A. baumannii accounted for 8.5%25 prevalence. Most of the A. baumannii isolated were from the male patients (75%25) within the age range of 33-48 years. Antibiotic susceptibility test using Kirby Bauer method in accordance with CLSI guidelines was done on 20 A. baumannii isolates. The isolates were more sensitive to levofloxacin (60%25), followed by Gentamicin (55%25), then Ciprofloxacin and Tetracycline (50%25) respectively. High level of resistance to Ceftriaxone (80%25), Cefepime (75%25), Ceftazidime (65%25), Piperacillin-Tazobactam (55%25), Ampicillin%252FSulbactam (60%25), Tigecycline (60%25), Meropenem (55%25) and Amikacin (60%25). This study revealed that 15 (75%25) of the A. baumannii were found to be multidrug-resistant. Therefore, antibiotic stewardship is necessary to combat further dissemination of this organism

Human cytomegalovirus: taking the strain

In celebrating the 60th anniversary of the first isolation of human cytomegalovirus (HCMV), we reflect on the merits and limitations of the viral strains currently being used to develop urgently needed treatments. HCMV research has been dependent for decades on the high-passage strains AD169 and Towne, heavily exploiting their capacity to replicate efficiently in fibroblasts. However, the genetic integrity of these strains is so severely compromised that great caution needs to be exercised when considering their past and future use. It is now evident that wild-type HCMV strains are not readily propagated in vitro. HCMV mutants are rapidly selected during isolation in fibroblasts, reproducibly affecting gene RL13, the UL128 locus (which includes genes UL128, UL130 and UL131A) and often the UL/b′ region. As a result, the virus becomes less cell associated, altered in tropism and less pathogenic. This problem is not restricted to high-passage strains, as even low-passage strains can harbour biologically significant mutations. Cloning and manipulation of the HCMV genome as a bacterial artificial chromosome (BAC) offers a means of working with stable, genetically defined strains. To this end, the low-passage strain Merlin genome was cloned as a BAC and sequentially repaired to match the viral sequence in the original clinical sample from which Merlin was derived. Restoration of UL128L to wild type was detrimental to growth in fibroblasts, whereas restoration of RL13 impaired growth in all cell types tested. Stable propagation of phenotypically wild-type virus could be achieved only by placing both regions under conditional expression. In addition to the development of these tools, the Merlin transcriptome and proteome have been characterized in unparalleled detail. Although Merlin may be representative of the clinical agent, high-throughput whole-genome deep sequencing studies have highlighted the remarkable high level of interstrain variation present in circulating virus. There is a need to develop systems capable of addressing the significance of this diversity, free from the confounding effects of genetic changes associated with in vitro adaptation. The generation of a set of BAC clones, each containing the genome of a different HCMV strain repaired to match the sequence in the clinical sample, would provide a pathway to address the biological and clinical effects of natural variation in wild-type HCMV

Velocity oscillations in confined channel flows of concentrated colloidal suspensions

We study the pressure-driven flow of concentrated colloids confined in glass micro-channels at the single particle level using fast confocal microscopy. For channel to particle size ratios $a/\bar{D} \lesssim 30$, the flow rate of the suspended particles shows fluctuations. These turn into regular oscillations for higher confinements ($a/\bar{D} \simeq 20$). We present evidence to link these oscillations with the relative flow of solvent and particles (permeation) and the effect of confinement on shear thickening.Comment: 4 pages, 6 figure