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Measurement of the Casimir torque
Intermolecular forces are pervasive in nature and give rise to various phenomena including surface wetting
1
, adhesive forces in biology
2
,
3
, and the Casimir effect
4
, which causes two charge-neutral, metal objects in vacuum to attract each other. These interactions are the result of quantum fluctuations of electromagnetic waves and the boundary conditions imposed by the interacting materials. When the materials are optically anisotropic, different polarizations of light experience different refractive indices and a torque is expected to occur that causes the materials to rotate to a position of minimum energy
5
,
6
. Although predicted more than four decades ago, the small magnitude of the Casimir torque has so far prevented direct measurements of it. Here we experimentally measure the Casimir torque between two optically anisotropic materials—a solid birefringent crystal (calcite, lithium niobite, rutile or yttrium vanadate) and a liquid crystal (5CB). We control the sign and strength of the torque, and its dependence on the rotation angle and the separation distance between the materials, through the choice of materials. The values that we measure agree with calculations, verifying the long-standing prediction that a mechanical torque induced by quantum fluctuations can exist between two separated objects. These results open the door to using the Casimir torque as a micro- or nanoscale actuation mechanism, which would be relevant for a range of technologies, including microelectromechanical systems and liquid crystals.
The theoretically predicted Casimir torque, which causes charge-neutral, birefringent materials to rotate towards a preferred alignment, is measured.
Journal Article
Stay up with Hugo Best : a novel
\"June Bloom is a broke, cynical twenty-nine-year-old writers' assistant on the late-night comedy show, Stay Up with Hugo Best. Hugo Best is in his sixties, a beloved icon of TV and humor, and a notorious womanizer. After he unexpectedly retires and a party is held for his now unemployed staff, June ends up at a dive bar for an open-mic night and prepares for the sad return to the anonymous comedian lifestyle. What she's not prepared for is a run-in with Hugo at that dive bar. Nor for the invitation that swiftly follows: Hugo asks June to come to his mansion in Greenwich for the long Memorial Day weekend. \"No funny business,\" he insists. June, in need of a job and money, confident she can handle herself, but secretly harboring the remains of a childhood crush on the charming older comedian and former role model, accepts. The exact terms of the visit are never spelled out, but June is realistic and clear-eyed enough to guess. Even so, as the weekend unfolds and the enigmatic Hugo gradually reveals himself, their dynamic proves to be much more complicated and less predictable than she expected.\"-- Amazon.
Book
Diagnostic accuracy of body mass index to identify obesity in older adults: NHANES 1999–2004
Background:
Body composition changes with aging lead to increased adiposity and decreased muscle mass, making the diagnosis of obesity challenging. Conventional anthropometry, including body mass index (BMI), while easy to use clinically may misrepresent adiposity. We determined the diagnostic accuracy of BMI using dual-energy X-ray absorptiometry (DEXA) in assessing the degree of obesity in older adults.
Methods:
The National Health and Nutrition Examination Surveys 1999–2004 were used to identify adults aged ⩾60 years with DEXA measures. They were categorized (yes/no) as having elevated body fat by gender (men: ⩾25%; women ⩾35%) and by BMI ⩾25 and ⩾30 kg m
−
2
. The diagnostic performance of BMI was assessed. Metabolic characteristics were compared in discordant cases of BMI/body fat. Weighting and analyses were performed per NHANES (National Health and Nutrition Examination Survey) guidelines.
Results:
We identified 4984 subjects (men: 2453; women: 2531). Mean BMI and % body fat was 28.0 kg m
−2
and 30.8% in men, and 28.5 kg m
−
2
and 42.1% in women. A BMI ⩾30 kg m
−
2
had a low sensitivity and moderately high specificity (men: 32.9 and 80.8%, concordance index 0.66; women: 38.5 and 78.5%, concordance 0.69) correctly classifying 41.0 and 45.1% of obese subjects. A BMI ⩾25 kg m
−2
had a moderately high sensitivity and specificity (men: 80.7 and 99.6%, concordance 0.81; women: 76.9 and 98.8%, concordance 0.84) correctly classifying 80.8 and 78.5% of obese subjects. In subjects with BMI <30 kg m
−
2
, body fat was considered elevated in 67.1% and 61.5% of men and women, respectively. For a BMI ⩾30 kg m
−
2
, sensitivity drops from 40.3% to 14.5% and 44.5% to 23.4%, whereas specificity remains elevated (>98%), in men and women, respectively, in those 60–69.9 years to subjects aged ⩾80 years. Correct classification of obesity using a cutoff of 30 kg m
−
2
drops from 48.1 to 23.9% and 49.0 to 19.6%, in men and women in these two age groups.
Conclusions:
Traditional measures poorly identify obesity in the elderly. In older adults, BMI may be a suboptimal marker for adiposity.
Journal Article
A new way to age : the most cutting-edge advances in antiaging
\"At 72, the ... author of Knockout and Ageless is back with ... insights and advice from the best and brightest minds in the field of anti-aging. Learn how to keep your hair shiny, your heart strong, your hormones renewed, and your mind as sharp as ever\"-- Provided by publisher.
Book
Accuracy of body mass index in diagnosing obesity in the adult general population
Background: Body mass index (BMI) is the most widely used measure to diagnose obesity. However, the accuracy of BMI in detecting excess body adiposity in the adult general population is largely unknown. Methods: A cross-sectional design of 13 601 subjects (age 20-79.9 years; 49% men) from the Third National Health and Nutrition Examination Survey. Bioelectrical impedance analysis was used to estimate body fat percent (BF% ). We assessed the diagnostic performance of BMI using the World Health Organization reference standard for obesity of BF% >25% in men and>35% in women. We tested the correlation between BMI and both BF% and lean mass by sex and age groups adjusted for race. Results: BMI-defined obesity (30 kg m- 2) was present in 19.1% of men and 24.7% of women, while BF% -defined obesity was present in 43.9% of men and 52.3% of women. A BMI30 had a high specificity (men=95% , 95% confidence interval (CI), 94-96 and women=99% , 95% CI, 98-100), but a poor sensitivity (men=36% , 95% CI, 35-37 and women=49% , 95% CI, 48-50) to detect BF% -defined obesity. The diagnostic performance of BMI diminished as age increased. In men, BMI had a better correlation with lean mass than with BF% , while in women BMI correlated better with BF% than with lean mass. However, in the intermediate range of BMI (25-29.9 kg m- 2), BMI failed to discriminate between BF% and lean mass in both sexes. Conclusions: The accuracy of BMI in diagnosing obesity is limited, particularly for individuals in the intermediate BMI ranges, in men and in the elderly. A BMI cutoff of30 kg m- 2 has good specificity but misses more than half of people with excess fat. These results may help to explain the unexpected better survival in overweight/mild obese patients.
Journal Article
Diagnostic performance of body mass index to identify obesity as defined by body adiposity: a systematic review and meta-analysis
Objective: We performed a systematic review and meta-analysis of studies that assessed the performance of body mass index (BMI) to detect body adiposity. Design: Data sources were MEDLINE, EMBASE, Cochrane, Database of Systematic Reviews, Cochrane CENTRAL, Web of Science, and SCOPUS. To be included, studies must have assessed the performance of BMI to measure body adiposity, provided standard values of diagnostic performance, and used a body composition technique as the reference standard for body fat percent (BF%) measurement. We obtained pooled summary statistics for sensitivity, specificity, positive and negative likelihood ratios (LRs), and diagnostic odds ratio (DOR). The inconsistency statistic (I2) assessed potential heterogeneity. Results: The search strategy yielded 3341 potentially relevant abstracts, and 25 articles met our predefined inclusion criteria. These studies evaluated 32 different samples totaling 31 968 patients. Commonly used BMI cutoffs to diagnose obesity showed a pooled sensitivity to detect high adiposity of 0.50 (95% confidence interval (CI): 0.43–0.57) and a pooled specificity of 0.90 (CI: 0.86–0.94). Positive LR was 5.88 (CI: 4.24–8.15), I 2=97.8%; the negative LR was 0.43 (CI: 0.37–0.50), I 2=98.5%; and the DOR was 17.91 (CI: 12.56–25.53), I 2=91.7%. Analysis of studies that used BMI cutoffs 30 had a pooled sensitivity of 0.42 (CI: 0.31–0.43) and a pooled specificity of 0.97 (CI: 0.96–0.97). Cutoff values and regional origin of the studies can only partially explain the heterogeneity seen in pooled DOR estimates. Conclusion: Commonly used BMI cutoff values to diagnose obesity have high specificity, but low sensitivity to identify adiposity, as they fail to identify half of the people with excess BF%.
Journal Article
Integrated Metabolo-Proteomic Approach to Decipher the Mechanisms by Which Wheat QTL (Fhb1) Contributes to Resistance against Fusarium graminearum
Resistance in plants to pathogen attack can be qualitative or quantitative. For the latter, hundreds of quantitative trait loci (QTLs) have been identified, but the mechanisms of resistance are largely unknown. Integrated non-target metabolomics and proteomics, using high resolution hybrid mass spectrometry, were applied to identify the mechanisms of resistance governed by the fusarium head blight resistance locus, Fhb1, in the near isogenic lines derived from wheat genotype Nyubai.
The metabolomic and proteomic profiles were compared between the near isogenic lines (NIL) with resistant and susceptible alleles of Fhb1 upon F. graminearum or mock-inoculation. The resistance-related metabolites and proteins identified were mapped to metabolic pathways. Metabolites of the shunt phenylpropanoid pathway such as hydroxycinnamic acid amides, phenolic glucosides and flavonoids were induced only in the resistant NIL, or induced at higher abundances in resistant than in susceptible NIL, following pathogen inoculation. The identities of these metabolites were confirmed, with fragmentation patterns, using the high resolution LC-LTQ-Orbitrap. Concurrently, the enzymes of phenylpropanoid biosynthesis such as cinnamyl alcohol dehydrogenase, caffeoyl-CoA O-methyltransferase, caffeic acid O-methyltransferase, flavonoid O-methyltransferase, agmatine coumaroyltransferase and peroxidase were also up-regulated. Increased cell wall thickening due to deposition of hydroxycinnamic acid amides and flavonoids was confirmed by histo-chemical localization of the metabolites using confocal microscopy.
The present study demonstrates that the resistance in Fhb1 derived from the wheat genotype Nyubai is mainly associated with cell wall thickening due to deposition of hydroxycinnamic acid amides, phenolic glucosides and flavonoids, but not with the conversion of deoxynivalenol to less toxic deoxynivalenol 3-O-glucoside.
Journal Article