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A slotted Y‐branch laser diode that emits two spectral modes at a difference frequency of about 1 THz is investigated in the context of photonic based cw‐THz measurements. The beating frequency of the emitted laser light can be tuned by ±10.5 GHz around 1 THz by changing the applied laser current, which allows for potentially fast measurements. A second spectral window of ±6.5 GHz was found at 850 GHz. Pointwise scanning of the difference frequency is demonstrated with thickness determination of HRFZ‐Si wafer samples as a possible application scenario. [ABSTRACT FROM AUTHOR]

Escitalopram is a dual serotonin reuptake inhibitor (SSRI) approved for the treatment of depression and anxiety disorders. It is the S-enantiomer of citalopram, and is responsible for the serotonin reuptake activity, and thus for its pharmacological effects. Previous studies pointed out that clinically efficacious doses of other SSRIs produce an occupancy of the serotonin reuptake transporter (SERT) of about 80% or more. The novel radioligand [123I]ADAM and single photon emission computer tomography (SPECT) were used to measure midbrain SERT occupancies for different doses of escitalopram and citalopram. Twenty-five healthy subjects received a single dose of escitalopram [5 mg ( n=5), 10 mg ( n=5), and 20 mg ( n=5)] or citalopram [(10 mg ( n=5) and 20 mg ( n=5)]. Midbrain SERT binding was measured with [123I]ADAM and SPECT on two study days, once without study drug and once 6 h after single dose administration of the study drug. The ratio of midbrain-cerebellum/cerebellum was the outcome measure (V3”) for specific binding to SERT in midbrain. Subsequently, SERT occupancy levels were calculated using the untreated baseline level for each subject. An E max model was used to describe the relationship between S-citalopram concentrations and SERT occupancy values. Additionally, four subjects received placebo to determine test–retest variability. Single doses of 5, 10, or 20 mg escitalopram led to a mean SERT occupancy of 60±6, 64±6, and 75±5%, respectively. SERT occupancies for subjects treated with single doses of 10 and 20 mg citalopram were 65±10 and 70±6%, respectively. A statistically significant difference was found between SERT occupancies after application of 10 and 20 mg escitalopram, but not for 10 and 20 mg citalopram. There was no statistically significant difference between the SERT occupancies of either 10 mg citalopram or 10 mg escitalopram, or between 20 mg citalopram and 20 mg escitalopram. E max was slightly higher after administration of citalopram (84%) than escitalopram (79%). In the test–retest study, a mean SERT “occupancy” of 4% was found after administration of placebo, the intraclass correlation coefficient was 0.92, and the repeatability coefficient was 0.25. SPECT and [123I]ADAM were used to investigate SERT occupancies after single doses of escitalopram or citalopram. The test–retest study revealed good reproducibility of SERT quantification. Similar SERT occupancies were found after administration of equal doses (in respect to mg) of escitalopram and citalopram, giving indirect evidence for a fractional blockade of SERT by the inactive R-citalopram. [ABSTRACT FROM AUTHOR]

Acid invertase is present in immature but absent from mature internodal tissue of sugar cane (Saccharum officinarum). The acid invertase content of immature tissue may be increased or decreased during 8 to 18 hour incubation periods in indoleacetic acid (IAA) and α-naphthalene acetic acid (NAA). Both compounds show an optimum effect, but the concentration giving optimum response varies in different batches of tissue, apparently as a function of prevailing environmental conditions. In certain instances, gibberellic acid (GA) reduced the invertase level, and this effect was partially reversed by IAA. When incubated in glucose or glucose plus glycine, the invertase content fell to a low level. Upon transfer to water for 6 hours the invertase content increased 2.8-fold for tissue pretreated with glucose and 11-fold for tissue pretreated with glucose plus glycine. It was concluded that a pool of invertase precursors was built up from glycine, but that formation of new enzyme molecules was prevented until glucose was removed. The presence of the auxin-sugar regulatory system for controlling invertase levels was demonstrated in tissue from the wild species, Saccharum spontaneum, in which acid invertase is found in mature tissue. The evolutionary and physiological significance of this observation is discussed. [ABSTRACT FROM AUTHOR]

We investigate quantum-dot (QD) lasers in an external cavity using Littrow and Littman configurations. Here, we report on a continuously tunable QD laser with a broad tuning range from 1047 to 1130 nm with high stability and efficient side mode suppression. The full-width at half-maximum of the laser line is 0.85 nm determined mainly by the quality of the external grating. This laser can be operated in a dual-mode modus, where the mode-spacing can be tuned continuously between 1.1 and 34 nm. Simultaneous emission of the two laser modes is shown by sum frequency generation experiments. [ABSTRACT FROM AUTHOR]