Heterodyne laser radiation detection at 891 GHz using josephson point contacts

Experiments were carried out to investigate the performance of a heterodyne detector at 891 GHz using a cw hydrogen cyanide laser as the local oscillator and Nb-Nb point contact Josephson junctions as mixing devices. Using a second off-tuned HCN laser as the signal, intermediate frequencies (IF's) up to a few MHz could be studied. Both pre-set and adjustable types of junction were used, and the latter, arranged so that radiation could be directly focussed onto them gave the best ultimate sensitivity. Dependence of the IF power on dc current bias and local oscillator power is described, and compared with simple theory. IF power varied linearly with signal power for signals less than 10-5 to 10-6 W. The mixer conversion efficiency was independent of IF. The sensitivity of the detector was a strong function of junction characteristics and ranged over several orders of magnitude in the junctions studied. Noise at the output was dominated by the room temperature preamplifier with a noise temperature of about 500 K. The smallest observed value for conversion loss of the junction was about 29 dB. This figure includes the signal input matching loss. The best sensitivity of the whole receiving system was equivalent to 1 × 10-17 W/Hz.Pour étudier les performances d'un détecteur hétérodyne à 891 GHz on a utilisé un laser continu HCN comme oscillateur local, et une jonction Josephson à contact à pointe Nb-Nb, comme mélangeur. On a pu réaliser des fréquences intermédiaires (IF) jusqu'à quelques MHz, en utilisant un autre laser HCN comme générateur de signal. On a employé à la fois des jonctions pré-réglées, et des jonctions ajustables. Ces dernières donnant la meilleure sensibilité car elles permettent de focaliser le rayonnement directement sur la jonction. On étudie l'influence du courant continu de polarisation, et de la puissance de l'oscillateur local sur la puissance IF. Celle-ci varie linéairement avec la puissance du signal pour des niveaux inférieurs à 10-5 ou 10 -6 W. Le rendement de conversion du mélangeur est indépendant de la fréquence intermédiaire. La sensibilité du détecteur dépend fortement des caractéristiques et s'étend sur plusieurs ordres de grandeurs pour les jonctions étudiées. Le bruit est essentiellement celui du préamplificateur à température ambiante avec une température de bruit de l'ordre de 500 K. Les pertes par conversion minimales sont de l'ordre de 29 dB. Elles incluent les pertes dues à la désadaptation à l'entrée. La meilleure sensibilité obtenue pour le système de réception est de 10-17 W/Hz

Immunostimulation in the treatment for chronic fatigue syndrome/myalgic encephalomyelitis

Chronic fatigue syndrome (CFS)/myalgic encephalomyelitis (ME) has long been associated with the presence of infectious agents, but no single pathogen has been reliably identified in all patients with the disease. Recent studies using metagenomic techniques have demonstrated the presence of thousands of microbes in the human body that were previously undetected and unknown to science. More importantly, such species interact together by sharing genes and genetic function within communities. It follows that searching for a singular pathogen may greatly underestimate the microbial complexity potentially driving a complex disease like CFS/ME. Intracellular microbes alter the expression of human genes in order to facilitate their survival. We have put forth a model describing how multiple species - bacterial, viral, and fungal - can cumulatively dysregulate expression by the VDR nuclear receptor in order to survive and thus drive a disease process. Based on this model, we have developed an immunostimulatory therapy that is showing promise inducing both subjective and objective improvement in patients suffering from CFS/ME

Immunostimulation in the era of the metagenome

Microbes are increasingly being implicated in autoimmune disease. This calls for a re-evaluation of how these chronic inflammatory illnesses are routinely treated. The standard of care for autoimmune disease remains the use of medications that slow the immune response, while treatments aimed at eradicating microbes seek the exact opposite-stimulation of the innate immune response. Immunostimulation is complicated by a cascade of sequelae, including exacerbated inflammation, which occurs in response to microbial death. Over the past 8 years, we have collaborated with American and international clinical professionals to research a model-based treatment for inflammatory disease. This intervention, designed to stimulate the innate immune response, has required a reevaluation of disease progression and amelioration. Paramount is the inherent conflict between palliation and microbicidal efficacy. Increased microbicidal activity was experienced as immunopathology-a temporary worsening of symptoms. Further studies are needed, but they will require careful planning to manage this immunopathology

The modification and calibration of a thermo-electric radiometer for power measurements at submillimetre wavelengths

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