14 research outputs found
Rapid extraction of volatile compounds from Citrus fruits using a microwave dry distillation
Three different extraction methods were used for a comparative study of essential oil (EO) from fresh Citrus peels: Traditional hydrodistillation (HD), cold pressing (CP) and innovative microwave âdryâ distillation or microwave-accelerated distillation (MAD). The microwave process offers significant advantages over conventional alternatives, viz. shorter distillation period (30 min vs. 3 h for hydrodistillation and 1 h for cold pressing); better yields (0.24% vs. 0.21% for HD and 0.054% for CP); environmental impact (energy charge is noticeably superior for performing HD and for mechanical motors (CP) than that necessary for quick MAD assay); cleaner features (as no remains creation and no solvent or water used); raises antibacterial properties ; and offers a more precious EO (with high amounts of oxygenated compounds).Keywords: Microwave extraction; Hydrodistillation; Cold pressing; Essential oil; Citru
BAs and boride III-V alloys
Boron arsenide, the typically-ignored member of the III-V arsenide series
BAs-AlAs-GaAs-InAs is found to resemble silicon electronically: its Gamma
conduction band minimum is p-like (Gamma_15), not s-like (Gamma_1c), it has an
X_1c-like indirect band gap, and its bond charge is distributed almost equally
on the two atoms in the unit cell, exhibiting nearly perfect covalency. The
reasons for these are tracked down to the anomalously low atomic p orbital
energy in the boron and to the unusually strong s-s repulsion in BAs relative
to most other III-V compounds. We find unexpected valence band offsets of BAs
with respect to GaAs and AlAs. The valence band maximum (VBM) of BAs is
significantly higher than that of AlAs, despite the much smaller bond length of
BAs, and the VBM of GaAs is only slightly higher than in BAs. These effects
result from the unusually strong mixing of the cation and anion states at the
VBM. For the BAs-GaAs alloys, we find (i) a relatively small (~3.5 eV) and
composition-independent band gap bowing. This means that while addition of
small amounts of nitrogen to GaAs lowers the gap, addition of small amounts of
boron to GaAs raises the gap (ii) boron ``semi-localized'' states in the
conduction band (similar to those in GaN-GaAs alloys), and (iii) bulk mixing
enthalpies which are smaller than in GaN-GaAs alloys. The unique features of
boride III-V alloys offer new opportunities in band gap engineering.Comment: 18 pages, 14 figures, 6 tables, 61 references. Accepted for
publication in Phys. Rev. B. Scheduled to appear Oct. 15 200