Explore the vast range of titles available.

Objective Bacteria play an important role in the onset and perpetuation of intestinal inflammation in inflammatory bowel disease (IBD). Unlike in Crohn's disease (CD), in which dysbiosis has been better characterised, in ulcerative colitis (UC), only small cohorts have been studied and showed conflicting data. Therefore, we evaluated in a large cohort if the microbial signature described in CD is also present in UC, and if we could characterise predominant dysbiosis in UC. To assess the functional impact of dysbiosis, we quantified the bacterial metabolites. Design The predominant microbiota from 127 UC patients and 87 age and sex-matched controls was analysed using denaturing gradient gel electrophoresis (DGGE) analysis. Differences were quantitatively validated using real-time PCR. Metabolites were quantified using gas chromatography–mass spectrometry. Results Based on DGGE analysis, the microbial signature previously described in CD was not present in UC. Real-time PCR analysis revealed a lower abundance of Roseburia hominis (p<0.0001) and Faecalibacterium prausnitzii (p<0.0001) in UC patients compared to controls. Both species showed an inverse correlation with disease activity. Short-chain fatty acids (SCFA) were reduced in UC patients (p=0.014), but no direct correlation between SCFA and the identified bacteria was found. Conclusions The composition of the fecal microbiota of UC patients differs from that of healthy individuals: we found a reduction in R hominis and F prausnitzii, both well-known butyrate-producing bacteria of the Firmicutes phylum. These results underscore the importance of dysbiosis in IBD but suggest that different bacterial species contribute to the pathogenesis of UC and CD.

The interaction of xylan, an abundant plant polysaccharide, with cellulose microfibrils is essential for secondary cell wall strength. A deeper understanding of these interactions is crucial both to improve our understanding of plant cell wall architecture and to design alternate strategies to overcome cellulose recalcitrance for the production of biofuels and sustainable biomaterials. Naturally occurring acetate or glucuronic acid substitutions on xylan have been shown to influence xylan-cellulose interactions. Here, we use unrestrained molecular dynamics simulations to determine the interactions with the (110) hydrophilic face of cellulose fibers of four different xylans. In the absence of cellulose, all xylans, independent of the substitution pattern, adopt a highly flexible threefold helical screw conformation. However, when xylan is spatially close to a cellulose surface 1,2 linked acetyl xylans (2AcX) adopt rigid twofold helical screw conformations. The 2AcX conformations are primarily stabilized by interactions between the acetylated oxygen and the glycosidic linkage with C-O6 of cellulose. In contrast, the glycosidic oxygens and acetyl decorations for 1,3 linked acetyl groups (3AcX) are oriented away from the cellulose surface and the 3AcX xylans maintain threefold helical screw conformations on the cellulose surface. Our results show that evenly spaced chemical functionalization (with acetyl groups) and the position of substitution (1,2) on xylan backbone play key roles in tuning the xylan-cellulose interactions to stabilize the twofold helical screw conformations of xylan on the cellulose surface. A comparison with previous experimental findings further suggests that 1,2 substitutions induce twofold helical screw conformations of xylan on the cellulose surface irrespective of the chemical nature of the substituent, while 1,3 substitutions primarily bind lignin in threefold helical screw conformations rather than cellulose in plant cell walls.

The fabrication of pure copper microstructures with submicron resolution has found a host of applications, such as 5G communications and highly sensitive detection. The tiny and complex features of these structures can enhance device performance during high-frequency operation. However, manufacturing pure copper microstructures remain challenging. In this paper, we present localized electrochemical deposition micro additive manufacturing (LECD- μ AM). This method combines localized electrochemical deposition (LECD) and closed-loop control of atomic force servo technology, which can effectively print helical springs and hollow tubes. We further demonstrate an overall model based on pulsed microfluidics from a hollow cantilever LECD process and closed-loop control of an atomic force servo. The printing state of the micro-helical springs can be assessed by simultaneously detecting the Z -axis displacement and the deflection of the atomic force probe cantilever. The results showed that it took 361 s to print a helical spring with a wire length of 320.11 μ m at a deposition rate of 0.887 μ m s −1 , which can be changed on the fly by simply tuning the extrusion pressure and the applied voltage. Moreover, the in situ nanoindenter was used to measure the compressive mechanical properties of the helical spring. The shear modulus of the helical spring material was about 60.8 GPa, much higher than that of bulk copper (∼44.2 GPa). Additionally, the microscopic morphology and chemical composition of the spring were characterized. These results delineate a new way of fabricating terahertz transmitter components and micro-helical antennas with LECD- μ AM technology.

Circularly polarized luminescence (CPL) has gained considerable attention in various systems and has rapidly developed into an emerging research field. To meet the needs of actual applications in diverse fields, a high luminescence dissymmetry factor (glum) and tunable optical performance of CPL would be the most urgent pursuit for researchers. Accordingly, many emerging CPL materials and various strategies have been developed to address these critical issues. Emissive cholesteric liquid crystals (CLCs), that is, luminescent self‐organized helical superstructures, are considered to be ideal candidates for constructing CPL‐active materials, as they not only exhibit high glum values, but also enable flexible optical control of CPL. This review mainly summarizes the characteristics of CPL based on CLCs as the bulk phase doped with different emitters, including aggregated induced emission molecules, conventional organic small molecules, polymer emitters, metal–organic complex emitters, and luminescent nanoparticles. In addition, the recent significant progress in stimulus‐responsive CPL based on emissive CLCs in terms of several types of stimuli, including light, electricity, temperature, mechanical force, and multiple stimuli is presented. Finally, a short perspective on the opportunities and challenges associated with CPL‐active materials based on the CLC field is provided. This review is anticipated to offer new insights and guidelines for developing CLC‐based CPL‐active materials for broader applications. Cholesteric liquid crystals (CLCs) with self‐organized helical superstructures have exhibited considerable advantages in terms of achieving high luminescence dissymmetry factors and tunable circularly polarized luminescence (CPL) properties. This review highlights the recent developments in CLC‐based CPL‐active materials doped with various emitters. In addition, stimulus‐responsive CPL based on emissive CLCs is systematically summarized.

Purpose Crossed helical gears have point contact and their surfaces are subject to high surface stress. Contact stress and root tooth stress are the most common sources of failure in crossed helical gear. This paper aims to study the load-carrying capacity and performance of crossed helical gear teeth with different gear tooth profiles. To overcome defects and reduce the sensitivity to small shaft angle changes. The combined tooth profile is designed to reduce the bending stresses, contact stresses and tooth deflection, and prevent pinion failure in the gearbox. Design/methodology/approach The principle of the method is a line contact is introduced instead of a point contact between two teeth in mesh with each other. The tooth surface of the helical gear is designed and cut by a modified tool. Higher normal pressure angles like 25° and 35° are used. The modified involute is accomplished to eliminate interference between the teeth. Engineering software packages have been applied to generate all crossed helical gears gear profiles. The modification is compounding curves consisting of an epicycloid-involute-hypocycloid gear teeth profile generated by the cutter modified. Findings The stresses in the crossed helical gear teeth profile were reduced by increasing the normal pressure angle values. Using a 35° pressure angle the enhancement percentage in contact stress and teeth fillet region will be about 29.345% and 15.421%, respectively. The best enhancement in a gear’s resistance is the epicycloid-involute-hypocycloid gear teeth profile. The enhancement was 32.610% and 18.588%. The skew in line of action in skewed helical gear will be sensitive when the crossing angles are small. Their teeth surface tends to be easily worn out; however, the wearing process will be reduced by using a proposed gear teeth profile. Practical implications The gear teeth to be modified are cut by a shaper process. The modifying rack cutter of this study can be used as a reference for creating a different helical gears sample. The helical teeth surface is modified to become an envelope of the other. This makes an original point contact change into a line contact. The epicycloid-involute-hypocycloid gear teeth profile is preferred for a higher contact ratio and a large load capacity. This work explicitly introduces a new method of kinematic consideration to improve the load capacity of crossed helical gear. Originality/value This paper showed some novel results by the unique shape of the rack-cutter designed to generate different helical angles and different gear positions. In the future, it will make valuable contributions to the further development of the dynamic performance of a crossed helical gear system through the study in the field of using asymmetric teeth profiles of helical gears with tip relief as the manner to enhance the crossed helical gear performance. Investigation of crossed helical gear by applying a predesigned parabolic function of transmission error enables the absorption of linear discontinuous functions caused by misalignment.

Efficient particle exhaust remains a key challenge in magnetic confinement fusion, particularly in stellarators, where divertor neutral pressures are typically low. Recently, exceptionally high neutral pressures-up to 2.4 Pa-were measured in the divertor of the Large Helical Device, exceeding theoretical predictions and previously observed stellarator values by an order of magnitude. We demonstrate that such high pressures can only be sustained through an additional particle exhaust channel formed by plasma condensation. At the same time, the divertor plasma is detached and exhibits strong hydrogen radiation. This divertor regime therefore appears to be an excellent candidate for fusion reactors based on the stellarator concept.

A topology optimization of a reducer’s helical gear was performed using the variable density method, with element density as the design variable, compliance as the objective, and constraints on volume fraction and structural equilibrium. The optimized geometry reduced mass by 25% while maintaining sufficient stiffness and strength. Static and modal analyses confirm that the design meets mechanical requirements and achieves the lightweighting goal. This approach demonstrates strong engineering applicability and provides a reference for similar component designs.

It is undeniable that in large-scale production, special-purpose reducers are increasingly being used instead of universal ones, which is certainly a cause for concern among manufacturers of universal reducers. However, in many applications, universal reducers are practically irreplaceable, as their various configurations - adapted for different mounting forms and positions - can meet nearly all customer requirements at an acceptable cost. This paper highlights the main advantages of using universal geared reducers with external helical gears.

Double-pipe helical heat exchangers (DPHHXs) are widely used for cooling and heating applications. In this study, a combination of two methods is used to enhance the performance of DPHHX. The thermal–hydraulic performance is investigated using a nanofluid of silicon dioxide and water (SiO 2 /water) as well as spring wire insert (SWI) experimentally and numerically. The numerical model is validated with the experimental results. The parameters such as Nusselt number, pressure drop, exergy efficiency, and thermal–hydraulic enhancement factor are investigated for Reynolds number range from 4500 to 7000. The results show the Nusselt number is enhanced with nanofluid employment and SWI. Nusselt number increases by 34% when 0.1% volume concentration of nanofluid is used and by 43.5% when spring wire is only used compared to base water. The configuration with a 0.3% volume concentration and SWI achieves the highest Nusselt number enhancement ratio, exhibiting a 174% increase compared to other configurations. In the same case, the pressure drop ratio reaches its peak at 157%. The exergy efficiency improves with an increase in nanoparticle volume concentration, with the 0.3% concentration with SWI showing the highest values, ranging from 54 to 65%. Among different concentrations, the SiO 2 /water nanofluid with a 0.2% volume concentration with SWI demonstrates the highest thermal–hydraulic enhancement factor, making it the optimal choice. The results prove that spring wire inert is more effective than nanofluid in the DPHHX. The contours, streamlines, and vectors of the temperature, velocity, and pressure distributions give more understanding for the heat transfer and fluid flow.

Most people think gears are a man-made invention; however, the shape of gears also exists in the flea hind leg kinematic mechanism [1]. This research utilized the flea hind tooth profile leg as a basis to fit the tooth profile of a virtual skewed rack cutter. The tooth profile of a virtual skewed rack cutter are created and applied to create helical gear pairs. The tooth surface for the rack cutter is adjusted so that the tooth thickness is maximal at the tooth center. The tooth thickness decreases progressively along the tooth surface longitudinal direction, resulting in a barrel-shaped tooth surface for the rack cutter. The modification method of the gear tooth surface can effectively avoid the problem of edge contact. Installation errors for the gear pair are simulated. The tooth contact analysis (TCA) method is utilized, and the kinematic error of the gear pair is then calculated. It is observed that the vertical component of the installation error in the shaft lead to larger kinematic errors. The values of the vertical component of the installation error at large and small angles were compared. The results show that the kinematic error curve remains unchanged, but as the axis assembly error angle becomes larger, the kinematic error value becomes larger. The finite element analysis method is conducted to explore the gear pair behavior after modification. All tooth contacts occur at the center of the curved surface, effectively avoiding edge contacts.