The unique physical and chemical properties of interfaces are governed by a finite depth that describes the transition from the topmost atomic layer to the properties of the bulk material. Thus, understanding the physical nature of interfaces requires detailed insight into the different structures, chemical compositions, and physical processes that form this interfacial region. Such insight has traditionally been difficult to obtain from experiments, as it requires a combination of structural and chemical sensitivity with spatial depth resolution on the nanometer scale. In this contribution, we present a vibrational spectroscopic approach that can overcome these limitations. By combining phase-sensitive sum and difference frequency-generation (SFG and DFG, respectively) spectroscopy and by selectively determining different nonlinear interaction pathways, we can extract precise depth information and correlate these to specific vibrationally resonant modes of interfacial species. We detail the mathematical framework behind this approach and demonstrate the performance of this technique in two sets of experiments on selected model samples. An analysis of the results shows an almost perfect match between experiment and theory, confirming the practicability of the proposed concept under realistic experimental conditions. Furthermore, in measurements with self-assembled monolayers of different chain lengths, we analyze the spatial accuracy of the technique and find that the precision can even reach the sub-nanometer regime. We also discuss the implications and the information content of such depth-sensitive measurements and show that the concept is very general and goes beyond the analysis of the depth profiles. The presented SFG/DFG technique offers new perspectives for spectroscopic investigations of interfaces in various material systems by providing access to fundamental observables that have so far been inaccessible by experiments. Here, we set the theoretical and experimental basis for such future investigations.

<p style="text-align: justify;">This study aimed to explore the perceived factors that influenced the success and challenges experienced when taking licensure examination among Bachelor of Science in Criminology graduates of a state university in the Philippines who failed in the Criminologist Licensure Examinations (CLE). Descriptive-correlational research design was utilized to analyze quantitative data, and Colaizzi’s descriptive phenomenology was used for the thematic analysis of qualitative data. The quantitative findings revealed that home and family factor has a high influence on the success in CLE, while student factor, school factor, review center factor, and personal factor have average influence. Further, ten clusters of themes emerged as factors that influence the success in CLE. Among them were interest and focus on the program, and availability of qualified and dedicated faculty. Among the themes that emerged as challenges were lack of preparedness for the exam because of one’s work, and personal and social pressures. There is a significant difference on the respondents’ perception towards the factors that influence the success in CLE when they are grouped according to sex. Regarding the challenges associated with preparing for and taking the CLE, a significant difference is only observed when respondents are grouped according to their civil status. Generally, married respondents have higher weighted means than the single ones. This implies that the identified challenges affected married respondents more than the single ones. These results can be used to make policies and initiate programs that would enhance graduates’ success in the exam by providing appropriate interventions and early remediations.</p>

Nonlinear (vibrational) microscopy has emerged as a successful tool for the investigation of molecular systems as it combines label-free chemical characterization with spatial resolution on the sub-micron scale. In addition to the molecular recognition, the physics of the nonlinear interactions allows in principle to obtain structural information on the molecular level such as molecular orientations. Due to technical limitations such as the relatively complex imaging geometry with the required oblique sample irradiation and insufficient sensitivity of the instrument this detailed molecular information is typically not accessible using widefield imaging. Here, we present, what we believe to be, a new microscope design that addresses both challenges. We introduce a simplified imaging geometry that enables the measurement of distortion-free widefield images with free space oblique sample irradiation achieving high spatial resolution (∼1 µm). Furthermore, we present a method based on a paired-pixel balanced detection system for sensitivity improvement. With this technique, we demonstrate a substantial enhancement of the signal-to-noise ratio of up to a factor of 10. While both experimental concepts presented in this work are very general and can, in principle, be applied to various microscopy techniques, we demonstrate their performance for the specific case of heterodyned, sum frequency generation (SFG) microscopy.

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