Optoelectronic cross-injection locking of a dual-wavelength photonic integrated circuit for low-phase-noise millimeter-wave generation.

We report on the stabilization of a 90-GHz millimeter-wave signal generated from a fully integrated photonic circuit. The chip consists of two DFB single-mode lasers whose optical signals are combined on a fast photodiode to generate a largely tunable heterodyne beat note. We generate an optical comb from each laser with a microwave synthesizer, and by self-injecting the resulting signal, we mutually correlate the phase noise of each DFB and stabilize the beatnote on a multiple of the frequency delivered by the synthesizer. The performances achieved beat note linewidth below 30 Hz.

Coherent terahertz photonics.

We present a review of recent developments in THz coherent systems based on photonic local oscillators. We show that such techniques can enable the creation of highly coherent, thus highly sensitive, systems for frequencies ranging from 100 GHz to 5 THz, within an energy efficient integrated platform. We suggest that such systems could enable the THz spectrum to realize its full applications potential. To demonstrate how photonics-enabled THz systems can be realized, we review the performance of key components, show recent demonstrations of integrated platforms, and give examples of applications.

Demonstration of a heterogeneously integrated III-V/SOI single wavelength tunable laser.

A heterogeneously integrated III-V-on-silicon laser is reported, integrating a III-V gain section, a silicon ring resonator for wavelength selection and two silicon Bragg grating reflectors as back and front mirrors. Single wavelength operation with a side mode suppression ratio higher than 45 dB is obtained. An output power up to 10 mW at 20 °C and a thermo-optic wavelength tuning range of 8 nm are achieved. The laser linewidth is found to be 1.7 MHz.

[Prevalence of dementia in Tuscany: results from four population-based epidemiological studies]. / La prevalenza della demenza in Toscana: i risultati di quattro studi epidemiologici di popolazione.

OBJECTIVE: to provide information on epidemiology of dementia in Tuscany needed to plan for dedicated health and social services. DESIGN: analysis of pooled baseline data from 4 population-based longitudinal studies. SETTING: 4 municipalities in Tuscany. PARTICIPANTS: 4,056 elderly subjects enrolled in 4 longitudinal studies. MAIN OUTCOME MEASURES: age- and sex-specific dementia prevalence rates and estimated number of demented people, by degree of cognitive impairment and BADL disability in the elderly population of Tuscany. RESULTS: out of the evaluated subjects, 293 are demented. Prevalence of dementia increases from about 1 % in the 65-69 age group to about 28 % in the 90+ age group both among women and men. About 43% of the demented study subjects suffer from severe mental deterioration (MMSE < 14) and56% are disabled in at least one Basic Activity of Daily Living (BADL). We estimate that about 19 thousand demented elderly men and 40 thousand demented elderly women are currently living in Tuscany of whom 26 thousand severely mentally impaired and 34 thousand disabled in at least one BADL. The resulting overall dementia prevalence standardised on the Italian 65+ population is 5,3% for men and 7,7% for women. CONCLUSIONS: these estimates could be used as a basis for the evaluation and the planning of social and health care services dedicated to demented people.

Insulin resistance in cognitive impairment: the InCHIANTI study.

OBJECTIVE: To test the association between cognitive impairment, with and without subcortical features, and insulin resistance in an elderly community-dwelling population. DESIGN: Cross-sectional wave of an epidemiologic longitudinal study (InCHIANTI). PARTICIPANTS: A total of 523 people, aged 70 to 90 years without diabetes mellitus or hyperglycemia, from the InCHIANTI cohort were included in the study. A total of 119 individuals had cognitive impairment (Mini-Mental State Examination [MMSE] score < 25), 21 of whom had both cognitive impairment and subcortical features (CI/SF+ group). Control groups contained 23 individuals with a history of stroke and 381 individuals with no cognitive impairment (no CI group, MMSE score > or = 25). Indicators of insulin resistance were the fasting plasma insulin level, insulin resistance index (Homeostasis Model Assessment of Insulin Resistance [HOMA-IR]), and insulin sensitivity index (Quantitative Insulin Sensitivity Check Index [QUICKI]). RESULTS: The insulin resistance profile of patients in the CI/SF+ group was similar to that of individuals who had experienced stroke, whereas the profile of individuals with cognitive impairment without subcortical features (CI/SF- group) was similar to that of individuals in the no CI group. Patients in the CI/SF- group showed insulin resistance comparable to individuals in the no CI group (age-adjusted P = .27, .19, and .64, respectively, for difference in fasting blood insulin level, HOMA-IR, and QUICKI in linear regression models) and lower than patients with stroke (age-adjusted P = .01, .02, and .07, respectively). On the contrary, patients in the CI/SF+ group had insulin resistance and sensitivity values similar to those of the stroke group (age-adjusted P = .80, .84, and .75, respectively, for difference in fasting blood insulin level, HOMA-IR, and QUICKI) but significantly different from those in the no CI group (age-adjusted P = .01, .03, and .02, respectively). CONCLUSIONS: Cognitive impairment with but not without subcortical features is associated with biochemical and clinical features of insulin resistance syndrome. In epidemiologic populations, insulin resistance might contribute to cognitive impairment through a vascular mechanism.

Vitamin E levels, cognitive impairment and dementia in older persons: the InCHIANTI study.

There is conflicting evidence that antioxidants contribute to maintaining cognitive function in elderly subjects. We investigated whether vitamin E plasma levels are related to the presence of dementia and cognitive impairment in a population-based cohort study conducted in Italy. A total of 1033 participants aged at least 65 years received clinical and neuropsychological examinations, donated blood for vitamin E analysis and had their diets assessed. Participants with plasma vitamin E levels in the bottom tertile had a significantly higher probability of being demented (OR 2.6, 95% CI 1.0-7.1) and also of suffering from cognitive impairment (OR 2.2, 95% CI 1.2-4.2) compared to those in the highest vitamin E tertile after adjustment for age, gender, education, lipid levels, energy intake, vitamin E intake, and smoking. This study supports the notion that higher vitamin E plasma levels might provide significant protection against cognitive impairment and dementia in elderly subjects.

Insulin resistance and executive dysfunction in older persons.

OBJECTIVES: To evaluate the association between insulin resistance (IR) and executive dysfunction in a large, population-based study of older persons without diabetes mellitus (DM) or dementia. DESIGN: Cross-sectional study. SETTING: Outpatient clinic in Greve in Chianti and Bagno a Ripoli, Italy. PARTICIPANTS: A total of 597 subjects aged 65 to 93 without DM or dementia. MEASUREMENTS: Anthropometric measurements; plasma fasting levels of glucose, insulin, cholesterol (total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol), and insulin-like growth factor-1 (IGF-1); homeostasis model assessment (HOMA) to estimate degree of IR; Trail Making Test (TMT) A; TMT-B; TMT-B minus TMT-A (DIFF B-A); and Mini-Mental State Examination (MMSE). RESULTS: IR (HOMA) was associated with longer TMT-B (correlation coefficient (r)=0.11; P=.006) and DIFF B-A times (r=0.10; P=.022). Subjects in the upper tertile of IR were older and had longer TMT-B and DIFF B-A than participants in the lowest tertile. After adjusting for age, sex, and years of formal education, IR was significantly correlated with TMT-A, TMT-B, and DIFF B-A. After adjusting for age, sex, education, body mass index, waist:hip girth ratio, HDL-C, triglycerides, IGF-1, hypertension, drug intake, and physical activity, the results did not significantly change. After introducing MMSE score into the model, IR continued to be an independent determinant of TMT-A (beta=11.005; P=.021), TMT-B (beta=28.379; P<.001), and DIFF B-A (beta=17.374; P=.011). CONCLUSION: IR is independently associated with frontal cortex function evidenced by poor TMT times in older persons without DM or dementia.