3,898 research outputs found
Effects of Torefaction with Counter-Flow Multi Baffle (COMB) Reactor and Electric Furnace on the Properties of Jabon (Anthocephalus cadamba) Pellets
No full textThe objective of this study was to improve the quality of jabon (Anthocephalus cadamba) wood pellets through torrefaction with Counter-Flow Multi-Baffle (COMB) reactor and electric furnace (EF). COMB is a reactor that can conduct torrefaction with a short residence time, approximately around 3 to 5 min. The torrefaction with COMB reactor was conducted at 260°C and 280°C C, with a residence time of 3 min. The torrefaction with EF used the temperature of 260°C and 280°C with a duration of 20 min. The pellet properties evaluated include the color changes, physical characteristics, and heating values. The result showed that the color of Jabon wood pellet was totally changed after torrefaction with COMB reactor reaching the highest overall color-change (∆E *) of 21,9 in the long pellets and 21,7 in the short pellets, while torrefaction with EF resulted in the highest ∆E* of 28,6 and 23,2, in the long and short pellets, respectively. The initial moisture content of the long and short pellets of Jabon wood were 12,41% and 12,33%. After torrefaction with COMB the moisture content decreased to 2,85% and 2,61%, while after torrefaction with EF the values decreased to 2,77% and 2,58%. The initial density of the long and short pellets were 1,05 g/cm3 and 0,97 g/cm3. The density decreased to 0,91 g/cm3 and 0,76 g/cm3 after torrefaction with COMB reactor, and decreased to 0,87 g/cm3 and 0,75 g/cm3 after torrefaction with EF. The research result also showed that the initial heating value of long and short pellets of 17,69 MJ/kg increased to 31,79 MJ/kg (long pellets) and 32.02 MJ/kg (short pellets) after torrefaction with COMB reactor, and increased to 19.74 MJ/kg (long pellets) and 19.99 MJ/kg (short pellets) after torrefaction with EF. Torrefaction with COMB reactor with shorter residence time resulted in a higher improvement in bioenergetic properties of jabon wood pellets in comparison to torrefaction with EF.Keywords: Anthocephalus cadamba, Counter-Flow Multi Baffle, torrefactio
Multiple pathways of plasmid DNA transfer in Helicobacter pylori
No full textMany Helicobacter pylori (Hp) strains carry cryptic plasmids of different size and gene content, the function of which is not well understood. A subgroup of these plasmids (e.g. pHel4, pHel12), contain a mobilisation region, but no cognate type IV secretion system (T4SS) for conjugative transfer. Instead, certain H. pylori strains (e.g. strain P12 carrying plasmid pHel12) can harbour up to four T4SSs in their genome (cag-T4SS, comB, tfs3, tfs4). Here, we show that such indigenous plasmids can be efficiently transferred between H. pylori strains, even in the presence of extracellular DNaseI eliminating natural transformation. Knockout of a plasmid-encoded mobA relaxase gene significantly reduced plasmid DNA transfer in the presence of DNaseI, suggesting a DNA conjugation or mobilisation process. To identify the T4SS involved in this conjugative DNA transfer, each individual T4SS was consecutively deleted from the bacterial chromosome. Using a marker-free counterselectable gene deletion procedure (rpsL counterselection method), a P12 mutant strain was finally obtained with no single T4SS (P12ΔT4SS). Mating experiments using these mutants identified the comB T4SS in the recipient strain as the major mediator of plasmid DNA transfer between H. pylori strains, both in a DNaseI-sensitive (natural transformation) as well as a DNaseI-resistant manner (conjugative transfer). However, transfer of a pHel12::cat plasmid from a P12ΔT4SS donor strain into a P12ΔT4SS recipient strain provided evidence for the existence of a third, T4SS-independent mechanism of DNA transfer. This novel type of plasmid DNA transfer, designated as alternate DNaseI-Resistant (ADR) mechanism, is observed at a rather low frequency under in vitro conditions. Taken together, our study describes for the first time the existence of three distinct pathways of plasmid DNA transfer between H. pylori underscoring the importance of horizontal gene transfer for this species
Self-compression of 4.9 µm pulses to sub-40 fs with 2 mJ energy in Zinc Sulfide
No full textNonlinear self-compression of few-cycle multi-mJ pulses at 4.9 µm in ZnS is presented. 80 fs input pulses are compressed to 37 fs with 2.1 mJ energy at a 1 kHz repetition rate. © 2024 The Author(s
Peningkatan Kualitas Pelet Tandan Kosong Kelapa Sawit melalui Torefaksi Menggunakan Reaktor Counter-Flow Multi Baffle (COMB)
No full textOil palm (Elaeis guineensis) empty fruit bunches (EFB) have not been utilized optimally. Currently, it is considered as a resource with low economic value. This biomass can be converted into bioenergy through a torrefaction process. Torrefaction is a mild pyrolysis at temperatures ranging between 200 and 300 °C, and it is generally performed under an inert atmosphere. The objective of this study was to evaluate the effects of torrefaction using Counter-Flow Multi Baffle (COMB) on the properties of oil palm EFB pellets. Torrefaction was conducted at 280 °C temperature with a residence time of 4 minutes. The results showed a decrease in the equilibrium moisture content and an increase in hydrophobicity after torrefaction using the COMB reactor. The change in the hygroscopic property could make the oil palm EFB pellet more stable against chemical oxidation and microbial degradation, hence self-heating and auto-ignition during storage could be prevented. The heating value of biomass increased after torrefaction. Torrefaction with the COMB reactor resulted in a heating value of 17.90 MJ/kg, which is comparable with the results of oxidative torrefaction (with longer residence time) of 18.28 MJ/kg. The results suggested that torrefaction using the COMB reactor could provide a great improvement in the quality of the bioenergetic properties of oil palm EFB pellets. However, the high ash content of the EFB pellets implied that the EFB pellets suitable for a small-scale application, but not yet for cofiring in power plants or as a feedstock for gasification.Keywords: Counter-Flow Multi Baffle; oil palm empty fruit bunches; renewable; torrefactionA B S T R A KTandan kosong kelapa sawit (Elaeis guineensis) belum dimanfaatkan secara optimal. Saat ini bahan tersebut masih dianggap sebagai sumber daya bernilai ekonomi rendah. Tandan kosong kelapa sawit (TKKS) dapat dikonversi menjadi bioenergi melalui proses torefaksi. Torefaksi merupakan proses pirolisis ringan pada suhu berkisar antara 200 dan 300 °C dan umumnya dilakukan di bawah kondisi inert. Penelitian ini bertujuan untuk mengetahui pengaruh torefaksi dengan reaktor Counter-Flow Multi Baffle (COMB) terhadap sifat-sifat pelet TKKS. Torefaksi dilakukan pada suhu 280 °C dengan waktu tinggal 4 menit. Hasil penelitian menunjukkan bahwa torefaksi menyebabkan penurunan kadar air kesetimbangan dan menjadi hidrofobik setelah torefaksi dengan reaktor COMB. Perbaikan sifat higroskopis dapat membuat pelet TKKS lebih stabil terhadap oksidasi kimia dan degradasi mikroba, sehingga pemanasan sendiri dan pembakaran spontan selama penyimpanan dapat dicegah. Nilai kalor biomassa meningkat setelah torefaksi. Torefaksi dengan reaktor COMB menghasilkan nilai kalor 17,90 MJ/kg, yang sebanding dengan hasil torefaksi oksidatif dengan waktu tinggal lebih lama, sebesar 18,28 MJ/kg. Hasil penelitian menunjukkan bahwa torefaksi dengan reaktor COMB dapat meningkatkan kualitas energi pelet TKKS. Tetapi pelet TKKS masih memiliki kadar abu yang tinggi sehingga biomassa hasil torefaksi belum sesuai untuk cofiring di pembangkit listrik atau sebagai bahan baku untuk gasifikasi.Kata kunci: Counter-Flow Multi Baffle; tandan kosong kelapa sawit; terbarukan; torefaksi
Toughening Ionic Polymer Using Bulky Alkylammonium Counterions and Comb Architecture
No full textIonic interactions in ionic polymers, such as ionomers,
polyelectrolytes,
and polyampholytes, contribute to toughness in systems with high mobility
and active ion dynamics, such as hydrogels and elastomers. However,
it remains challenging to toughen rigid polymers through ionic interactions
without lowering their elastic modulus through plasticization. Here,
we present a strategy for toughening without sacrificing the elastic
modulus by combining a comb polymer with bulky ammonium counterions.
We designed and synthesized ionic comb polymers with oligoethylene
glycol side chains and carboxylic acids in each monomer unit of the
polynorbornene backbone, neutralized by trialkylamines, ranging from
ethyl to octyl. The counterion size in ionic comb polymers influenced
the mechanical properties of tensile testingnot the elongation
at break and the elastic modulus but the ultimate strength and toughness.
The ionic comb polymer containing heptylammonium counterions displayed
the highest toughness of 77 MJ m–3. Tensile studies
at various strain rates demonstrated a rate-dependent difference between
heptyl- and octylammonium counterions. This result suggests that the
heptylammonium counterion acted as a sacrificial bond by providing
a moderate dissociation rate that was slightly slower than that of
the octylammonium counterion, leading to toughening
Optical Phase Lock Loop as High-Quality Tuneable Filter for Optical Frequency Comb Line Selection
No full textThis paper describes an optical phase lock loop
(OPLL) implemented as an ultraselective optical frequency comb
line filter. The OPLL is based on a photonic integrated circuit (PIC)
fabricated for the first time through a generic foundry approach.
The PIC contains a distributed Bragg reflector (DBR) laser whose
frequency and phase are stabilized by reference to an optical frequency
comb generator. The OPLL output is a single-mode DBR
laser line; other comb lines and noise at the output of the OPLL
filter are attenuated by >58 dB below the peak power of the OPLLfilter
output line. The OPLL bandwidth is up to 200 MHz, giving
a filter quality factor greater than 1,000,000. The DBR laser can
be tuned over 1 THz (8 nm), enabling different comb lines to be
selected. Locking to a comb line with a frequency offset precisely
selectable between 4 and 12 GHz is also possible. The coherence
between the DBR laser and the comb lines is demonstrated by
measurements of the heterodyne signal residual phase noise level,
which is below −100 dBc/Hz at 5 kHz offset from the carrier. The
OPLL-filter output can be up to 6 dB higher than the peak power
of the comb line to be isolated by the filter. This optical gain is a
unique characteristic which can significantly improve the SNR of
communication or spectroscopy systems. This OPLL is envisaged
to be used for high purity, tuneable microwave, millimetre-wave,
and THz generation
InP Photonic Integrated Circuit for 6.7GHz Spaced Optical Frequency Comb Generator
No full textWe have demonstrated a novel approach to photonically integrated optical frequency comb generation on Indium Phosphide (InP) using generic foundry platforms. The optical comb utilized a recirculating loop technique to generate 59 comb lines (within a 20 dB power envelope) which are separated by 6.7 GHz frequency spacing. All comb lines exhibit strong phase coherence as characterized by low phase noise measurements of -105 dBc/Hz at 100 kHz. The choice of InP as an integration platform allowed for an immediate optical amplification of the modulated sideband tones. This approach reduced the requirement for external high-power RF amplifiers and therefore made the entire system more compact and power efficient. The amplified recirculating loop comb occupied 6 x 0.7 mm2 area of InP chip and consisted of electro-optic phase modulator (EOPM) and semiconductor optical amplifier (SOA) components embedded within a short (12 mm long) waveguide loop, such that the round-trip loop frequency corresponding to the loop optical length equated to 6.7 GHz. Modulation frequencies equal to the round-trip loop frequency were used to generate broad comb spans
Multi-delay, phase coherent pulse pair generation for precision Ramsey-frequency comb spectroscopy
No full textWe demonstrate the generation of phase-stable mJ-pulse pairs at programmable inter-pulse delays up to hundreds of nanoseconds. A detailed investigation of potential sources for phase shifts during the parametric amplification of the selected pulses from a Ti:Sapphire frequency comb is presented, both numerically and experimentally. It is shown that within the statistical error of the phase measurement of 10 mrad, there is no dependence of the differential phase shift over the investigated inter-pulse delay range of more than 300 ns. In combination with nonlinear upconversion of the amplified pulses, the presented system will potentially enable short wavelength (<100 nm), multi-transition Ramsey-frequency comb spectroscopy at the kHz-level. © 2013 Optical Society of America
Correction to: Chamoun et al., Bacterial pathogenesis and interleukin-17: interconnecting mechanisms of immune regulation, host genetics, and microbial virulence that influence severity of infection
No full textChamoun MN, Blumenthal A, Sullivan MJ, Schembri MA, Ulett GC. 2018. Bacterial pathogenesis and interleukin-17: interconnecting mechanisms of immune regulation, host genetics, and microbial virulence that influence severity of infection. Critical Reviews in Microbiology. https://doi.org/10.1080/1040841X.2018.1426556.
When the above article was first published online, the below three corrections were missed.
The author ‘Antje Blumenthal’ was wrongly affiliated to the affiliation “cSchool of Chemistry and Molecular Biosciences, and Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Australia”. Now this affiliation has been removed for this author.
The affiliation ‘bTranslational Research Institute, The University of Queensland Diamantina Institute, Woolloongabba, Australia’ of the author ‘Antje Blumenthal’ should read ‘bThe University of Queensland Diamantina Institute, Translational Research Institute, Brisbane, Australia’.
In Table 3, the sentence ‘Benefit of manipulating IL-17 levels to improve immunization strategies M. tuberculosis’ should read “Benefit of manipulating IL-17 levels to improve immunization strategies against M. tuberculosis”.No Full Tex
Generation of 22-mJ, 2.0-ps Pulses from a 1-kHz Ho:YLF Regenerative Chirped Pulse Amplifier
No full textWe report a CW-pumped Ho:YLF regenerative amplifier (RA) delivering pulses with 22.5-mJ energy and 2.0-ps duration at 1 kHz. The RA emitting at 2051 nm is broadband-seeded and implemented in a chirped pulse amplification system. © 2024 The Author(s
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