A positive temperature coefficient is the term which has been used to indicate that an increase in solubility occurs as the temperature is raised, whereas a negative coefficient indicates a decrease in solubility with rise in temperature.

Effect of Temperature

Biodegradable composites based on lignocellulosic fibers—An overview

We report a study of self-assembled beta-pleated sheets in B. mori silk fibroin films using thermal analysis and infrared spectroscopy. B. mori silk fibroin may stand as an exemplar of fibrous proteins containing crystalline beta-sheets. Materials were prepared from concentrated solutions (2−5 wt % fibroin in water) and then dried to achieve a less ordered state without beta-sheets. Crystallization of beta-pleated sheets was effected either by heating the films above the glass transition temperature (Tg) and holding isothermally or by exposure to methanol. The fractions of secondary structural components including random coils, alpha-helices, beta-pleated sheets, turns, and side chains were evaluated using Fourier self-deconvolution (FSD) of the infrared absorbance spectra. The silk fibroin films were studied thermally using temperature-modulated differential scanning calorimetry (TMDSC) to obtain the reversing heat capacity. The increment of the reversing heat capacity ΔCp0(Tg) at the glass transition fo...

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Determining Beta Sheet Crystallinity in Fibrous Proteins by Thermal Analysis and Infrared Spectroscopy

Fogging occurs when moisture condensation takes the form of accumulated droplets with diameters larger than 190 nm or half of the shortest wavelength (380 nm) of visible light. This problem may be effectively addressed by changing the affinity of a material’s surface for water, which can be accomplished via two approaches: i) the superhydrophilic approach, with a water contact angle (CA) less than 5°, and ii) the superhydrophobic approach, with a water CA greater than 150°, and extremely low CA hysteresis. To date, all techniques reported belong to the former category, as they are intended for applications in optical transparent coatings. A well-known example is the use of photocatalytic TiO2 nanoparticle coatings that become superhydrophilic under UV irradiation. Very recently, a capillary effect was skillfully adopted to achieve superhydrophilic properties by constructing 3D nanoporous structures from layer-by-layer assembled nanoparticles. The key to these two “wet”-style antifogging strategies is for micrometer-sized fog drops to rapidly spread into a uniform thin film, which can prevent light scattering and reflection from nucleated droplets. Optical transparency is not an intrinsic property of antifogging coatings even though recently developed antifogging coatings are almost transparent, and the transparency could be achieved by further tuning the nanoparticle size and film thickness. To our knowledge, the antifogging coatings may also be applied to many fields that do not require optical transparency, including, for example, paints for inhibiting swelling and peeling issues and metal surfaces for preventing corrosion. These types of issues, which are caused by adsorption of moisture, are hard to solve by the superhydrophilic approach because of its inherently “wet” nature. Thus, a “dry”-style antifogging strategy, which consists of a novel superhydrophobic technique that can prevent moisture or microscale fog drops from nucleating on a surface, is desired. Recent bionic researches have revealed that the self-cleaning ability of lotus leaves and the striking ability of a water-strider’s legs to walk on water can be attributed to the ideal superhydrophobicity of their surfaces, induced by special microand nanostructures. To date, the biomimetic fabrication of superhydrophobic microand/or nanostructures has attracted considerable interest, and these types of materials can be used for such applications as self-cleaning coatings and stain-resistant textiles. Although a superhydrophobic technique inspired by lotus leaves is expected to be able to solve such fogging problems because the water droplets can not remain on the surface, there are no reports of such antifogging coatings. Very recently, researchers from General Motors have reported that the surfaces of lotus leaves become wet with moisture because the size of the fog drops are at the microscale—so small that they can be easily trapped in the interspaces among micropapillae. Thus, lotuslike surface microstructures are unsuitable for superhydrophobic antifogging coatings, and a new inspiration from nature is desired for solving this problem. In this communication, we report a novel, biological, superhydrophobic antifogging strategy. It was found that the compound eyes of the mosquito C. pipiens possess ideal superhydrophobic properties that provide an effective protective mechanism for maintaining clear vision in a humid habitat. Our research indicates that this unique property is attributed to the smart design of elaborate microand nanostructures: hexagonally non-close-packed (ncp) nipples at the nanoscale prevent microscale fog drops from condensing on the ommatidia surface, and hexagonally close-packed (hcp) ommatidia at the microscale could efficiently prevent fog drops from being trapped in the voids between the ommatidia. We also fabricated artificial compound eyes by using soft lithography and investigated the effects of microand nanostructures on the surface hydrophobicity. These findings could be used to develop novel superhydrophobic antifogging coatings in the near future. It is known that mosquitoes possess excellent vision, which they exploit to locate various resources such as mates, hosts, and resting sites in a watery and dim habitat. To better understand such remarkable abilities, we first investigated the interaction between moisture and the eye surface. An ultrasonic humidifier was used to regulate the relative humidity of the atmosphere and mimic a mist composed of numerous tiny water droplets with diameters less than 10 lm. As the fog was C O M M U N IC A IO N

The dry-style antifogging properties of mosquito compound eyes and artificial analogues prepared by soft lithography: a superhydrophobic state with high adhesive force

Trees, and their derivative products, have been used by societies around the world for thousands of years. Contemporary construction of tall buildings from timber, in whole or in part, suggests a growing interest in the potential for building with wood at a scale not previously attainable. As wood is the only significant building material that is grown, we have a natural inclination that building in wood is good for the environment. But under what conditions is this really the case? The environmental benefits of using timber are not straightforward; although it is a natural product, a large amount of energy is used to dry and process it. Much of this can come from the biomass of the tree itself, but that requires investment in plant, which is not always possible in an industry that is widely distributed among many small producers. And what should we build with wood? Are skyscrapers in timber a good use of this natural resource, or are there other aspects of civil and structural engineering, or large-scale infrastructure, that would be a better use of wood? Here, we consider a holistic picture ranging in scale from the science of the cell wall to the engineering and global policies that could maximise forestry and timber construction as a boon to both people and the planet.

The wood from the trees: The use of timber in construction

Microfibrilated cellulose as a model for soft colloid flocculation with polyelectrolytes

Electron paramagnetic resonance (EPR) and optical absorption spectra of Cr3+ ions in Calcium alumino borate (CaAB) glasses have been studied. The EPR spectra exhibit weak resonance signal at g ≈ 4.50 and intense resonance signal at g ≈ 1.98. A sharp resonance signal at g ≈ 1.97 was also observed at lower concentrations of chromium. The concentration dependence of the linewidth of the resonance signal at g ≈ 1.98 suggests the formation of Cr3+ ion clusters by magnetic superexchange interactions. The temperature dependence of the peak to peak intensity and the linewidth of the resonance signal at g ≈ 1.98 suggests that the exchange interactions between Cr3+ ions in the present sample were antiferromagnetic in nature with Neel temperature, TN = 233 K. From the number of spins participating in the resonance at g ≈ 1.98, the paramagnetic susceptibility (χ) was calculated at different temperatures (233–295 K). A plot of 1/χ and T was found to obey Curie-Weiss law with negative Curie temperature. By measuring the relative intensities of the resonance signal at g ≈ 1.98, at different temperatures, the value of antiferromagnetic coupling constant (J) has been estimated. The optical absorption spectrum of chromium doped CaAB glass exhibits four bands, characteristic of Cr3+ ions, in nearly octahedral symmetry. From the band positions, the crystal field splitting parameter, Dq and the Racah interelectronic repulsion parameters, B and C were evaluated. The optical band gap (Eopt) and the Urbach energy (ΔE) were calculated from the ultraviolet absorption edges.

Inter-fibre contacts in random fibrous materials: experimental verification of theoretical dependence on porosity and fibre width

Viral disease outbreaks have been always a threat to global public health making affordable, rapid and accurate diagnostics highly important tools to slow down the spread of viruses and decrease the mortality rate. Point-of-care (POC) diagnostics have emerged as a strong tool for the diagnosis of viral infections, especially in countries where health-care systems are inadequate to provide proper services to all citizens. According to the World Health Organization, an ideal POC diagnostic must be Affordable, Sensitive, Specific, User-friendly, Rapid/Robust, Equipment-free and Deliverable (ASSURED). This review surveys carefully each ASSURED criterion and identifies where existing viral POC diagnostics fail to meet these criteria. Given the widespread concern with plastic pollution, we also propose the addition of 'disposability' to the existing ASSURED criteria and consider the letter "D" as the representative of both Deliverable and Disposable. Next, the POC tests used for the diagnosis of several common human viral infections which met all the ASSURED criteria (ASSURED-compliant) are described in detail. Finally, the future of ASSURED-compliant POC diagnostics, capable of generating comparable results to the viral diagnostic gold standards, is discussed.

ASSURED-compliant point-of-care diagnostics for the detection of human viral infections

Due to an equipment error, the values for the energy consumption of samples which were subjected to the milling process (presented in Table 2) are incorrect in the original publication. The value for sample M-20 is 20.2 kWh/kg and for sample M-40 is 33.2 kWh/kg.

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Evaluation of properties and specific energy consumption of spinifex-derived lignocellulose fibers produced using different mechanical processes

This paper proposes an analytical model for calculating the number of fibre–fibre contacts per unit fibre length from the cross-sectional dimensions of the fibres in a sheet and sheet density. This model has been verified with data of the number of fibre–fibre contacts measured directly in handsheets. The measured fibre–fibre contacts in the handsheets were classified into full and partial contacts. The model best fits this data when 1.5 partial contacts are equated to one full contact. A plot of measured versus predicted equivalent full contacts produced a linear correlation with a slope of 0.99 and correlation coefficient of R
 2
  = 0.93. The model was used to derive expressions for the fraction of the available fibre surface, which is bonded to other fibres, a quantity called the Relative Bonded Area (RBA). The validity of the model was checked using experimental data for RBA. RBA was determined both by nitrogen adsorption (

 
$$ {\hbox{RBA}}_{{\hbox{N}}_2 } $$
 ) and by scattering coefficient (RBAsc). The extrapolation method of Ingmanson and Thode to determine S
 0, the scattering coefficient of an unbonded sheet, proved to be inaccurate. We estimated S
 0 for some samples from their linear relationship between scattering coefficient and nitrogen adsorption. The new model accurately predicted both 
$$ {\hbox{RBA}}_{{\hbox{N}}_{\hbox{2}} } $$
 and RBAsc.

Warren Batchelor

Papers

Microfibrilated cellulose as a model for soft colloid flocculation with polyelectrolytes

Inter-fibre contacts in random fibrous materials: experimental verification of theoretical dependence on porosity and fibre width

ASSURED-compliant point-of-care diagnostics for the detection of human viral infections

Evaluation of properties and specific energy consumption of spinifex-derived lignocellulose fibers produced using different mechanical processes

An analytical model for number of fibre-fibre contacts in paper and expressions for relative bonded area (RBA)