A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν ~ 1–5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Here, we present a strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based on intracavity difference frequency generation. Room temperature continuous wave emission at 3.41 THz with a side-mode suppression ratio of 30 dB and output power up to 14 μW is achieved with a wall-plug efficiency about one order of magnitude higher than previous demonstrations. With this highly efficient design, continuous wave, single mode THz emissions with a wide frequency tuning range of 2.06–4.35 THz and an output power up to 4.2 μW are demonstrated at room temperature from two monolithic three-section sampled grating distributed feedback-distributed Bragg reflector lasers.

This paper presents a continuous reactive distillation process using solid acid catalysts to produce furfural from synthetic and real ( pre-hydrolysate liquor (PHL) from wood chip digestion) feeds containing xylose.The reactive distillation process provides a unique advantage of immediate furfural separation from the reaction zone as it is formed, thus minimizing the formation of undesired by-products (e.g., oligomers of furfural/humins) from subsequent furfural condensation reactions. A comprehensive experimental study was carried out using synthetic xylose feeds containing a mixture of pure xylose, water, and sulfolane as a solvent. Among various solid acid catalysts screened for their ability to produce furfural from dehydration of xylose, the zeolite H-mordenite (Si/Al = 10) gave the highest furfural yield (>75%). During this process, the aqueous feed was introduced at the top of the column, and xylose was dehydrated to furfural which was co-distilled with water out of the top of the column. The high-boiling sulfolane, with dissolved undesired byproducts, was collected at the bottom of the column. Steam-stripping was found to be helpful in effective separation of furfural from the reaction zone, thus further enhancing furfural yield. This study was extended to using authentic aqueous PHL feed. Salts present in this feed resulted in significant catalyst deactivation. Pre-treatment of the PHL feed with ion-exchange resin was found to be effective in achieving furfural yields of ∼75%. An in situ catalyst regeneration method was demonstrated successfully and resulted in achieving extended catalyst lifetime and furfural yield, similar to that obtained with synthetic xylose feeds. † Electronic supplementary information (ESI) available. See

We report on the design and performance of multi-stack InAs/InGaAs sub-monolayer (SML) quantum dots (QD) based infrared photodetectors (SML-QDIP). SML-QDIPs are grown with the number of stacks varied from 2 to 6. From detailed radiometric characterization, it is determined that the sample with 4 SML stacks has the best performance. The s-to-p (s/p) polarized spectral response ratio of this device is measured to be 21.7%, which is significantly higher than conventional Stranski-Krastanov quantum dots (∼13%) and quantum wells (∼2.8%). This result makes the SML-QDIP an attractive candidate in applications that require normal incidence.

Meta-heuristic approaches are general algorithmic framework, often nature-inspired and designed to solve NP-complete optimization problems in cellular manufacturing systems and has been a growing research area for the past two decades. This paper discusses various metaheuristic techniques such as evolutionary approach, Ant colony optimization, simulated annealing, Tabu search and other recent approaches, and their applications to the vicinity of group technology/cell formation (GT/CF) problem in cellular manufacturing. The nobility of this paper is to incorporate various prevailing issues, open problems of meta-heuristic approaches, its usage, comparison, hybridization and its scope of future research in the aforesaid area.

Purpose Service triads refer to tripartite relationships in which client firms serve their customers through third-party service providers. The purpose of this paper is to systematically review the nascent but fast-growing literature on service triads to explore the broad themes along which the literature has grown, and to identify the gaps and future research opportunities. Design/methodology/approach Systematic literature review (SLR) approach is adopted to retrieve, select, and synthesise relevant service triads studies. A citation network analysis on the corpus resulting from the SLR identified the core articles of the literature. Findings The SLR uncovered ten themes of research along the articles’ objectives, theories and methodologies. The classification framework of service triads, the roles of customers and providers, the size of the provider, triadic risks, controlling service delivery and service quality, regulated triads, the stability of the triads, and cross-country, cross-culture triads emerged as significant under-researched areas. Originality/value The paper illustrates research trends and provides insights into the neglected and under-researched problems of service triads. This is the first SLR on service triads.

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A heterogeneous quantum cascade laser, consisting of multiple stacks of discrete wavelength quantum cascade stages, emitting in 5.9-10.9 µm, wavelength range is reported. The broadband characteristics are demonstrated with a distributed-feedback laser array, emitting at fixed frequencies at room temperature, covering an emission range of ~760 cm(-1), which is ~59% relative to the center frequency. By appropriate choice of a strained AlInAs/GaInAs material system, quantum cascade stage design and spatial arrangement of stages, the distributed-feedback array has been engineered to exhibit a flat threshold current density across the demonstrated range.

Engel's biopsychosocial model, based in systems theory, assumes the reciprocal influence of biological, psychological, and social factors on one another and on mental and physical health. However, the model's application to scientific study is limited by its lack of specificity, thus constraining its implementation in training and healthcare environments. The Biobehavioral Family Model (BBFM) is one model that can facilitate specification and integration of biopsychosocial conceptualization and treatment of illness. The model identifies specific pathways by which family relationships (i.e., family emotional climate) impact disease activity, through psychobiological mechanisms (i.e., biobehavioral reactivity). Furthermore, it is capable of identifying positive and negative effects of family process in the same model, and can be applied across cultural contexts. The BBFM has been applied to the study of child health outcomes, including pediatric asthma, and adult health, including for underserved primary care patients, minoritized samples, and persons with chronic pain, for example. The BBFM also serves as a guide for training and clinical practice; two such applications are presented, including the use of the BBFM in family medicine residency and child and adolescent psychiatry fellowship programs. Specific teaching and clinical approaches derived from the BBFM are described in both contexts, including the use of didactic lecture, patient interview guides, assessment protocol, and family-oriented care. Future directions for the application of the BBFM include incorporating temporal dynamics and developmental trajectories in the model, extending testable theory of family and individual resilience, examining causes of health disparities, and developing family-based prevention and intervention efforts to ameliorate contributing factors to disease. Ultimately, research and successful applications of the BBFM could inform policy to improve the lives of families, and provide additional support for the value of a biopsychosocial approach to medicine.