A Novel Approach for Room-Temperature Intersubband Transition in GaN HEMT for Terahertz Applications

Terahertz (THz) technology has attracted tremendous attention recently due to its promising applications in various domains such as medical, biological, industrial imaging, broadband, safety, communication, radar, space science, and so on. Due to non-availability of powerful sources and highly sensitive and efficient detectors, the so-called THz gap remains largely unfilled. Despite seamless efforts from electronics and photonics technology researchers, the desired level of technology development to fill the THz gap still remains a challenge. GaN-based HEMT structures have been investigated as potential THz sources and detectors by a number of researchers. This chapter presents a very new and versatile mechanism for electrical tuning of intersubband transitions (ISBT) GaN high electron mobility transition (HEMT) devices. ISBT phenomena are usually demonstrated in photonic devices like a quantum cascade laser (QCL). Here we explore ISBT in an electronic GaN HEMT device. Conventional photonic devices like a QCL are operated at cryogenic temperature to minimize thermal effect. Tuning the conduction band through external gate bias is an advantage of an HEMT device for room temperature (RT) THz applications. This chapter demonstrates the theoretical and experimental novel ISBT phenomenon in GaN HEMT is for potential ambient applications in the THz range

IL-1β Promotes TGF-β1 and IL-2 Dependent Foxp3 Expression in Regulatory T Cells

Earlier, we have shown that GM-CSF-exposed CD8α− DCs that express low levels of pro-inflammatory cytokines IL-12 and IL-1β can induce Foxp3+ Tregs leading to suppression of autoimmunity. Here, we examined the differential effects of IL-12 and IL-1β on Foxp3 expression in T cells when activated in the presence and absence of DCs. Exogenous IL-12 abolished, but IL-1β enhanced, the ability of GM-CSF-exposed tolerogenic DCs to promote Foxp3 expression. Pre-exposure of DCs to IL-1β and IL-12 had only a modest effect on Foxp3− expressing T cells; however, T cells activated in the absence of DCs but in the presence of IL-1β or IL-12 showed highly significant increase and decrease in Foxp3+ T cell frequencies respectively suggesting direct effects of these cytokines on T cells and a role for IL-1β in promoting Foxp3 expression. Importantly, purified CD4+CD25+ cells showed a significantly higher ability to maintain Foxp3 expression when activated in the presence of IL-1β. Further analyses showed that the ability of IL-1β to maintain Foxp3 expression in CD25+ T cells was dependent on TGF-β1 and IL-2 expression in Foxp3+Tregs and CD25− effectors T cells respectively. Exposure of CD4+CD25+ T cells to IL-1β enhanced their ability to suppress effector T cell response in vitro and ongoing experimental autoimmune thyroidits in vivo. These results show that IL-1β can help enhance/maintain Tregs, which may play an important role in maintaining peripheral tolerance during inflammation to prevent and/or suppress autoimmunity

The pattern of needle stick injury among health care workers at West Bengal

Introduction: Health care workers (HCWs) are at increased risk of infection with blood-borne pathogens; because of occupational exposure. Objectives: The objective of the following study is to assess the occurrence of needle stick injury (NSI) among HCWs, various factors responsible for NSI, the circumstances under which they occur and explored the responses of the HCWs after an injury. Materials and Methods: A descriptive hospital based observational epidemiological study, cross-sectional in design was conducted in indoor and Out-patient Departments of Surgery, Medicine and Gynaecology and Obstetrics of Burdwan Medical College and Hospital from June 2012 to August 2012 using a pre-designed pre-tested semi-structured self-administered anonymous questionnaire among senior residents, junior residents, house-staffs, internees, nursing staff and nursing students and laboratory technicians. Results: 132 (53.0%) reported NSI in the preceding 1 year in the health care facility. Nurses and nursing students had the highest percentage (42.4%). Only 40.2% HCWs were wearing gloves at the time of NSI. Recapping of needles was the most common cause implicated in causing NSI. 49.2% HCWs took action instantly after an NSI. Conclusion: Occurrence of NSI among the HCWs in West Bengal was high. Information, education and communication materials should be displayed prominently at the places of work