Composition of the teat canal and intramammary microbiota of dairy cows subjected to antimicrobial dry cow therapy and internal teat sealant

Antimicrobial dry cow therapy (DCT) is an important component of mastitis control programs aimed to eliminate existing intramammary infections and prevent the development of new ones during the dry period. However, to what extent the microbiota profiles of different niches of the udder change during the dry period and following administration of DCT remains poorly understood. Therefore, the main objective of the present study was to qualitatively evaluate dynamics of the microbiota of teat canal (TC) and mammary secretions (i.e., milk and colostrum) of healthy udder quarters subjected to DCT using a long-acting antimicrobial product, containing penicillin G and novobiocin, in combination with internal teat sealant. To this end, TC swabs (n = 58) and their corresponding milk (n = 29) and colostrum samples (n = 29) were collected at the time of drying off and immediately after calving from clinically healthy udder quarters of Holstein dairy cows from a commercial dairy farm. All samples were subjected to DNA extraction and high-throughput sequencing of the V1–V2 hypervariable regions of bacterial 16S rRNA genes. Overall, shifts were more pronounced within the microbiota of mammary secretions than the TC. In particular, microbiota of colostrum samples collected immediately after calving were less species-rich compared with the pre-DCT milk samples. Proportions of several bacterial genera belonging to the phylum Proteobacteria, including Pseudomonas, Stenotrophomonas, and unclassified Alcaligenaceae, were enriched within the microbiota of colostrum samples, whereas Firmicutes genera, including Butyrivibrio, unclassified Clostridiaceae, and unclassified Bacillales, were overrepresented in pre-DCT milk microbiota. Apart from shifts in the proportion of main bacterial genera and phyla, qualitative analysis revealed a high degree of commonality between pre-DCT and postpartum microbiota of both niches of the udder. Most importantly, a considerable number of bacterial genera and species commonly regarded as mastitis pathogens or opportunists (or both), including Staphylococcus spp., unclassified Enterobacteriaceae, and Corynebacterium spp., were shared between pre-DCT and postpartum microbiota of mammary secretions. Percentage of shared bacterial genera and species was even higher between pre-DCT and postpartum microbiota of TC samples, suggesting that the DCT approach of the present study had limited success in eliminating a considerable proportion of bacteria during the dry period.     

In Vitro Propagation of XXY Undifferentiated Mouse Spermatogonia: Model for Fertility Preservation in Klinefelter Syndrome Patients

Klinefelter syndrome (KS) is characterized by a masculine phenotype, supernumerary sex chromosomes (usually XXY), and spermatogonial stem cell (SSC) loss in their early life. Affecting 1 out of every 650 males born, KS is the most common genetic cause of male infertility, and new fertility preservation strategies are critically important for these patients. In this study, testes from 41, XXY prepubertal (3-day-old) mice were frozen-thawed. Isolated testicular cells were cultured and characterized by qPCR, digital PCR, and flow cytometry analyses. We demonstrated that SSCs survived and were able to be propagated with testicular somatic cells in culture for up to 120 days. DNA fluorescent in situ hybridization (FISH) showed the presence of XXY spermatogonia at the beginning of the culture and a variety of propagated XY, XX, and XXY spermatogonia at the end of the culture. These data provide the first evidence that an extra sex chromosome was lost during innate SSC culture, a crucial finding in treating KS patients for preserving and propagating SSCs for future sperm production, either in vitro or in vivo. This in vitro propagation system can be translated to clinical fertility preservation for KS patients.     

A Novel Self-aligned and Maskless Process for Formation of Highly Uniform Arrays of Nanoholes and Nanopillars

Fabrication of a large area of periodic structures with deep sub-wavelength features is required in many applications such as solar cells, photonic crystals, and artificial kidneys. We present a low-cost and high-throughput process for realization of 2D arrays of deep sub-wavelength features using a self-assembled monolayer of hexagonally close packed (HCP) silica and polystyrene microspheres. This method utilizes the microspheres as super-lenses to fabricate nanohole and pillar arrays over large areas on conventional positive and negative photoresist, and with a high aspect ratio. The period and diameter of the holes and pillars formed with this technique can be controlled precisely and independently. We demonstrate that the method can produce HCP arrays of hole of sub-250 nm size using a conventional photolithography system with a broadband UV source centered at 400 nm. We also present our 3D FDTD modeling, which shows a good agreement with the experimental results.     

A Review on Applications of Integrated Terahertz Systems

A review on Terahertz end-to-end systems with an emphasis on integrated approaches is presented.Four major catalogs of THz integrated systems,including THz comm...     

Scaling effects for flow in micro-channels: Variable property,viscous heating,velocity slip,and temperature jump

This paper reports closed form solutions, based on perturbation techniques, for fully developed, both hydrodynamically and thermally, slip-flow forced convection in both parallel plate and circular microchannels subject to isothermal wall boundary condition. Scaling effects, including variable property, viscous dissipation, velocity slip, and temperature jump are studied in detail. The results are not only applicable to gaseous flow in the slip-flow regime but also can be used for no-slip liquid flow in microchannels.     

A 4-stage 60-GHz low-noise amplifier in 65-nm CMOS with body biasing to control gain, linearity, and input matching

A 4-stage 60-GHz low-noise amplifier is designed and laid out in a 65?nm CMOS technology. Transmission lines are used to realize the power matching networks at the input, output, and between the stages. Based on foundry-provided models, extensive electromagnetic simulations with Momentum^? (a 2.5D simulator by Agilent) are performed on transmission lines, capacitors and I/O pads to model the behavior of the circuit at mm-wave frequencies. Furthermore, body biasing is used as a technique to control gain variability, linearity performance, and input matching of the designed LNA. Post-layout simulation results show that the LNA achieves a maximum gain of 21.3?dB at 60?GHz while consuming 20?mW from a 1.2?V supply. By changing the body bias voltage of the transistors in the two intermediate stages, the overall gain varies from 14 to 21.3?dB providing more than 7?dB of gain range. Adjusting the body biasing of the transistors in the last stage, results in a maximum IIP3 of more than 2?dBm for the overall amplifier. Also, the input return loss of the LNA is controlled by changing the bulk voltage of the input transistor in the first stage.     

A comprehensive review on numerical approaches to simulate heat transfer of turbulent supercritical CO2 flows

Abstract

Extensive computational investigations have been performed to obtain more detailed information about the peculiar phenomena of turbulent supercritical carbon dioxide (sCO₂) flow as ideal heat transfer fluids in various thermal engineering applications. This paper reviews the simulation techniques used and discusses their advantages, shortcomings and applicability. Not only is a comprehensive inspection on various computational approaches provided, but also the model refinements are suggested. Direct Numerical Simulations (DNS) provides valuable and reliable information about the thermohydraulics of turbulent sCO₂ flows, in particular within the near-wall region, which well interprets the observed heat transfer enhancement and deterioration with property variations, flow acceleration and buoyancy discussed. However, DNS is not feasible when it comes to high Reynolds number flows with complex geometries encountered in practical applications because of the drastically increasing computational cost. Reynolds-Averaged Navier-Stokes (RANS) modeling is able to fill the gap with acceptable accuracy and becomes the mainstream for turbulent sCO₂ heat transfer simulations. The flow and heat transfer behaviors of turbulent sCO₂ can be simulated using RANS modeling leading to acceptable predictions. However, the performance variation is considerable for different models and for the same model of changing operating conditions, model generality is not reached. In addition, some treatments implemented into the RANS models for constant property fluids are not appropriate for variable-property sCO₂ flows, causing inconsistency on the mixed convection predictions. Variable turbulent Prandtl number and more advanced calculation schemes for buoyancy production of turbulent kinetic energy are strongly recommended. Also, more appropriate treatments for damping functions are demanded to enable the model properly respond to the local property changes, particularly near the wall. Much simpler models with far less computational cost based upon the two-layer theory are being developed to achieve the generality. While this is promising, the examinations are still limited to the certain conditions and some model parameters need to be calibrated against the DNS data, which definitely reduces the model universality since DNS only covers a limited range of operating conditions. Developing more generic and reliable RANS models is still the main focus of simulation techniques used for turbulent sCO₂ heat transfer.     

An Efficient Measure for Quantification of Nonlinearity in Chemical Engineering Processes Based on I/O Steady-State Loci

Nonlinearity is virtually ubiquitous in chemical engineering plants, and assessing the degree of nonlinearity involved in a process is of special interest for process control purposes. In this paper, we introduce a simple nonlinearity measure to quantify the extent of nonlinearity in a dynamic system based on its normalized steady-state input/output loci. Our nonlinearity measure obviates the limitations of previous metrics in terms of computational effort and correct identification of highly nonlinear relationships. The measure is satisfactorily applicable to various I/O relationships—from truly linear to sinusoidal, for instance. In order to illustrate the efficiency of the proposed measure, four numerical examples concerning a double-effect evaporator, a jacketed continuously stirred tank reactor (CSTR) with an irreversible reaction, a CSTR involving van de Vusse reactions, and the Henson–Seborg–Pottmann CSTR are presented.