Vacuum cooling (VC) is a cooling technology for moist and porous foodstuffs with superiority in cooling rate, uniformity and hygiene, and low energy consumption. However, there are still some ...disadvantages that weaken the competitiveness of industrial applications such as the inevitable mass loss and uneven cooling in different parts of leafy vegetables. In order to improve the performance of VC, many efforts have been performed.
In this review, the basic information of VC and the main applications for fruit, vegetables and meat products as well as limitations are described first. Improvements for enhancing performances of this technology in terms of operation processes including pre-treatment, technical optimization and integration, as well as equipment upgrade, and optimized operation conditions such as final pressure and pressure reduction rate are discussed. In addition, the limitation and further prospects of VC in the food industry are also mentioned.
The findings presented in this review demonstrated that optimizing operation processes and controlling operation conditions can effectively improve the performance of VC including mass loss, cooling rate and energy consumption and temperature distribution. However, many enhancing strategies still have limitation for applied in the food industry. Future trends of VC are the study of moisture migration characteristics based on food microstructure and multi-functional optimization of VC process or system. It is hoped that the current review can provide some guidance for further developments of the VC technology.
•Contemporary applications of vacuum cooling to foods are presented.•Limitations in application and performance of vacuum cooling are discussed.•Innovative operation processes to improve vacuum cooling technology are assessed.•Strategies to refine operation conditions of vacuum cooling are outlined.•Key research trends comprise moisture migration and multi-functional optimization.
Killing the cMSSM softly Bechtle, Philip; Camargo-Molina, José Eliel; Desch, Klaus ...
The European physical journal. C, Particles and fields,
02/2016, Volume:
76, Issue:
2
Journal Article
Peer reviewed
Open access
We investigate the constrained Minimal Supersymmetric Standard Model (cMSSM) in the light of constraining experimental and observational data from precision measurements, astrophysics, direct ...supersymmetry searches at the LHC and measurements of the properties of the Higgs boson, by means of a global fit using the program
Fittino
. As in previous studies, we find rather poor agreement of the best fit point with the global data. We also investigate the stability of the electro-weak vacuum in the preferred region of parameter space around the best fit point. We find that the vacuum is metastable, with a lifetime significantly longer than the age of the Universe. For the first time in a global fit of supersymmetry, we employ a consistent methodology to evaluate the goodness-of-fit of the cMSSM in a frequentist approach by deriving
p
values from large sets of toy experiments. We analyse analytically and quantitatively the impact of the choice of the observable set on the
p
value, and in particular its dilution when confronting the model with a large number of barely constraining measurements. Finally, for the preferred sets of observables, we obtain
p
values for the cMSSM below 10 %, i.e. we exclude the cMSSM as a model at the 90 % confidence level.
Asphaltenes challenge nearly all analytical techniques because of their immense polydispersity in molecular composition and structure. This operationally defined fraction of crude oil, insoluble in ...n-alkanes but soluble in aromatic solvents, is known to concentrate in vacuum residues and islinked to fouling and deposition issues. However, presence and subsequent characterization of asphaltenes are seldom discussed in conventional/unconventional distillate fractions. Here, we isolate asphaltenes from conventional (<593 °C/1099 F) and unconventional (>593 °C) distillation cuts and provide molecular-level characterization by electrospray ionization and atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry as a function of boiling point. Our results indicate that asphaltene molecular composition starts in the vacuum gas oil range and extends into vacuum residues. Moreover, we report that distillable asphaltene composition exists as both highly polar (heteroatom rich), aliphatic (atypical asphaltenes) species as well as condensed aromatic structures (classical asphaltenes). As a function of distillation temperature, asphaltene compounds exhibit structural trends consistent with thermal cracking that starts between 510 and 538 °C, increases between 538 and 593 °C, and is readily observed at temperatures up to 700 °C. Above 600 °C, low molecular weight compounds (expected to boil at much lower temperatures) that are n-heptane insoluble are detected across all heteroatom classes. Results herein suggest that these compounds are formed through structural rearrangement of archipelago asphaltenes because of thermal cracking reactions that occur during distillation and precipitate as asphaltenes. We report the isolation and mass spectral characterization of asphaltenes isolated from distillation cuts and propose that quantification of asphaltenes in distillates is critical to predict and prevent problems related to catalyst deactivation.
Display omitted
•Basic degradation kinetics of TCEP in VUV system fits pseudo-first order reaction.•Radical oxidation is the dominant mechanism for TCEP degradation by VUV.•Incomplete degradation of ...TCEP generates phosphate-core organic products.•Early stage products have lower toxicity than TCEP or their further products.
Organophosphorus esters (OPEs), a series of high production volume chemicals, receive increasing concerns due to their occurrence in worldwide aquatic environment and resistance to conventional biological water treatment processes. Degradation of tris(2-chloroethyl) phosphate (TCEP) was tested with 185 + 254 nm ultraviolet irradiation treatment. Transformation of TCEP followed a pseudo-first order kinetics with an apparent rate constant at 1.65 × 10−3 s−1 when TCEP0 = 3.51 μM, 185 vacuum ultraviolet (VUV) irradiation intensity = 0.24 mW cm−2. Degradation experiments with wavelength screening, radical scavenging and kinetic calculation revealed that the radical-based oxidation induced by 185 nm VUV was the dominant mechanism with a reaction rate constant kOH-TCEP at (3.2 ± 0.3) × 108 M−1 s−1. Radical-based addition and substitution of TCEP generated intermediate products with phosphate backbone at early stage (0–20 min). Based on the toxicology analysis including reactive oxygen species and apoptosis of Escherichia coli, these early stage products have lower toxicity than TCEP or their further small molecule products. Variable pH value and natural organic matters/anions affected the efficiency of VUV, while intrinsic VUV screening and radicals scavenging were two key inhibition mechanisms. VUV induced a radical-based oxidation of TCEP, and it will be a promising treatment method for transforming and detoxifying micro-pollutants from water.
Vacuum pyrolysis deposition (VPD) has been used to create an ultrastable polymer glass having a fictive temperature T f of as much as 57 K below the nominal glass transition temperature of the ...thermally rejuvenated polymer. Amorphous fluoropolymer films 300 to 700 nm thick were created by VPD followed by characterization of the thermal response using rapid-scanning chip calorimetry. The deposition was performed for substrates held at temperatures from 30.0 °C (303.2 K) to 116.7 °C (389.9 K) corresponding to approximately 0.75 to 0.97 times the limiting fictive temperature T f ′ ≈ T g of the same material determined by cooling then heating at 600 K/s. Consistent with literature observations for small molecules that are vapor deposited in similar conditions relative to the material T g, large enthalpy overshoots are observed, typical of both highly aged and ultrastable glasses. The 57 K reduction in T f for the VPD polymers is greater than prior reports for physical vapor deposition of small molecules to form ultrastable glasses as well as greater than the T f reductions seen in ambers from 20 million to over 200 million years of age. The potential of using such materials to investigate systems extremely deep into the glassy condition is discussed.
Pomegranate juice having 17.5% total soluble solids (TSS) content was evaporated to 40%TSS by ohmic heating assisted vacuum evaporation (OVE; 7.5 V/cm, 10 V/cm and 12.5 V/cm) and vacuum evaporation ...(VE) methods. Thermodynamics’ first law and second law analyses were conducted for different TSS contents (20–40%) by taking into account of two different control boundaries; in terms of process boundary (PB) and system boundary (SB). Energy efficiency, specific water removal rate (SWRR) and exergy efficiency reached maximum values for 30% TSS content, then it decreased. It was determined that energetic and exergetic efficiencies of SB were lower than those of PB. For the same TSS content, exergy efficiency value increased and improvement potential (IP) value decreased as the voltage gradient increased. Since highest energy consumption (5844.20 ± 29.89 J) was determined at 40% TSS content for 7.5 V/cm (p < 0.05) this process condition need the improvement most. It can be concluded that OVE method used the energy more efficiently than VE method for the purpose of the concentration of pomegranate juice.
•Ohmic heating and vacuum processes were integrated (OVE).•Pomegranate juice was concentrated from 17.5% to 40% TSS content.•Energy and exergy analyses were performed both for system and process boundaries.•OVE at high voltage gradients were more efficient than conventional evaporation.•Highest energy and exergy efficiencies were obtained by OVE at 12.5 V/cm.
•Vacuum pyrolysis characteristics are studied to better understand organics pyrolysis.•Vacuum pyrolysis process is optimized by response surface methodology (RSM).•Pyrolysis products as oil, gas and ...residual are recycled by a reasonable route.
Recycling rare metal tantalum from waste tantalum capacitors (WTCs) is significant to alleviate the shortage of tantalum resource. However, environmental problems will be caused if the organic materials from WTCs are improperly disposed. This study presented a promising vacuum pyrolysis technology to recycle the organic materials from WTCs. The organics removal rate could reach 94.32wt% according to TG results. The optimal parameters were determined as 425°C, 50Pa and 30min on the basis of response surface methodology (RSM). The oil yield and residual rate was 18.09wt% and 74.94wt%, respectively. All pyrolysis products can be recycled through a reasonable route. Besides, to deeply understand the pyrolysis process, the pyrolysis mechanism was also proposed based on the product and free radical theory. This paper provides an efficient process for recycling the organic material from WTCs, which can facilitate the following tantalum recovery.
The application potential of cellulose nanofibril (CNF) aerogels has been hindered by the slow and costly freeze‐ or supercritical drying methods. Here, CNF aerogel membranes with attractive ...mechanical, optical, and gas transport properties are prepared in ambient conditions with a facile and scalable process. Aqueous CNF dispersions are vacuum‐filtered and solvent exchanged to 2‐propanol and further to octane, followed by ambient drying. The resulting CNF aerogel membranes are characterized by high transparency (>90% transmittance), stiffness (6 GPa Young's modulus, 10 GPa cm3 g−1 specific modulus), strength (97 MPa tensile strength, 161 MPa m3 kg−1 specific strength), mesoporosity (pore diameter 10–30 nm, 208 m2 g−1 specific surface area), and low density (≈0.6 g cm−3). They are gas permeable thus enabling collection of nanoparticles (for example, single‐walled carbon nanotubes, SWNT) from aerosols under pressure gradients. The membranes with deposited SWNT can be further compacted to transparent, conductive, and flexible conducting films (90% specular transmittance at 550 nm and 300 Ω ◻−1 sheet resistance with AuCl3‐salt doping). Overall, the developed aerogel membranes pave way toward use in gas filtration and transparent, flexible devices.
Facile ambient preparation of cellulose nanofibril (CNF) aerogel membranes is presented. Their use in collection of single‐walled carbon nanotubes (SWNT) from a gas stream is demonstrated to prepare flexible, transparent, and conductive films. These results point a direction for scalable preparation of aerogels and demonstrate their potential for applications involving capturing aerosol particles and transparent, flexible electronics.
TiO2 has been well studied as an ultraviolet (UV) photocatalyst and electrode material for lithium‐ion rechargeable batteries. Recent studies have shown that hydrogenated TiO2 displayed better ...photocatalytic and lithium ion battery performances. Here it is demonstrated that the photocatalytic and battery performances of TiO2 nanocrystals can be successfully improved with a facile low‐temperature vacuum process. These TiO2 nanocrystals extend their optical absorption far into the visible‐light region, display nanometer‐scale surface atomic rearrangement, possess superoxide ion characteristics at room temperature without light irradiation, show a 4‐fold improvement in photocatalytic activity, and has 30% better performance in capacity and charge/discharge rates for lithium ion battery. This facile method could provide an alternative and effective approach to improve the performance of TiO2 and other materials towards their practical applications.
A facile vacuum treatment of TiO2 nanocrystals significantly improves their photocatalytic and lithium‐ion battery performance due to dramatic changes in their structural, optical, electronic, and chemical properties.
This paper discusses the effect of temperature polarization in Vacuum Membrane Distillation (VMD). The main motivation for using VMD in this work is that this module configuration is much simpler and ...more suitable for this kind of investigation than the other MD configurations such as Direct Contact Membrane Distillation (DCMD). The coupling between heat and mass transfer mechanisms at the feed-membrane interface is presented from a theoretical point of view. In addition, a new simple graphical method and a mathematical model for determining VMD flux are presented. The two methods used in evaluating the extent of temperature polarization effect on water vapor flux (flux sensitivity factors and temperature polarization coefficient (TPC)) are also analyzed and compared. The effect of integrating a heat recovery system in a large scale module on the TPC coefficient has also been studied and presented in this paper.
•This work focused on studying the temperature polarization (TP) effect on flux in VMD.•Experimental data were used to validate the developed mathematical model.•Accurate prediction was achieved.•Flux sensitivity factors and TP Coefficient (TPC) were analyzed and compared.•The effect of TP was also studied for large scale modules having a heat recovery system.
PDF
