A more compact photoacoustic imaging system to detect periodontitis

Photoacoustic imaging has shown value in periodontal disease, but the large size of conventional photoacoustic transducers prevents imaging of more posterior teeth, i.e., molars. Here, we report a clinical hockey stick-style transducer repurposed for photoacoustic (PA) via an integrated fiber bundle. The shape of the hockey stick transducer facilitates imaging of the 1st pre-molars in contrast to conventional photoacoustic transducer designs. This tool was then deployed for photoacoustic imaging of periodontal disease and the periodontal pocket via a food-grade contrast agent (cuttlefish ink). We characterized the resolution and imaging range and then validated the system with a swine model and human subjects. We could image four additional teeth per quadrant with the smaller design versus a commercial photoacoustic transducer. Three raters evaluated the performance of the hockey stick transducer. The measurements between the probing and the PA methods were blinded, but the outcomes were highly correlated. We showed a bias of ~0.3 mm for the imaging-based technique versus conventional probing. In addition, the inter-reliability was over 0.60 for three different raters of varying experience suggesting that this approach to evaluating dental health is teachable and reproducible. Finally, we demonstrated the utility in a human subject and can image teeth much more posterior in the mouth than with conventional photoacoustic transducers.

Beyond the hockey stick: Climate lessons from the Common Era

More than two decades ago, my coauthors, Raymond Bradley and Malcolm Hughes, and I published the now iconic “hockey stick” curve. It was a simple graph, derived from large-scale networks of diverse climate proxy (“multiproxy”) data such as tree rings, ice cores, corals, and lake sediments, that captured the unprecedented nature of the warming taking place today. It became a focal point in the debate over human-caused climate change and what to do about it. Yet, the apparent simplicity of the hockey stick curve betrays the dynamicism and complexity of the climate history of past centuries and how it can inform our understanding of human-caused climate change and its impacts. In this article, I discuss the lessons we can learn from studying paleoclimate records and climate model simulations of the “Common Era,” the period of the past two millennia during which the “signal” of human-caused warming has risen dramatically from the background of natural variability.

Evaluation of the visibility of peri-implant bone defects using ultrasonography with two types of probes

Background: The aim of the present study was to evaluate the efficacy of intraoral and extraoral ultrasonography evaluations performed with two different types of probes (linear and “hockey stick”) for the visibility of peri-implant bone defects. Material and methods: Fourteen implants were inserted into sheep heads. Peri-implant bone defects were created without knowing the depth, which served as the gold standard for the defects. The defects were scanned with two different probe types (linear and hockey stick probes) extraorally and intraorally, using two different ultrasonography systems. For intra- and interobserver agreements for each probe types, Kappa coefficients were calculated. Results: The lowest ICC values were found in both intra- (ICC = 0.696) and interobserver reliability (ICC = 0.762) obtained with the extraorally used linear probe. There was a high agreement with the gold standard when using hockey sticky probes intraorally. For both linear probes, there were no significant differences in agreement among the two observers and the gold standard (p >0.05). Conclusions: High agreement was found when using high-frequency hockey stick probes intraorally, which means that they can be used with good effect for the evaluation of the visibility of peri-implant bone defects. To the best of our knowledge, this study is the first one on this subject. Thus, it can be stated that US can be an alternative method of examining defects. However, further studies are needed to evaluate the effectiveness of US in visualizing peri-implant bone defects.

On the u☆-U Relationship in the Stable Atmospheric Boundary Layer over Arctic Sea Ice

A relationship between the friction velocity u☆ and mean wind speed U in a stable atmospheric boundary layer (ABL) over Arctic sea ice was considered. To that aim, the observations collected during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment were used. The observations showed the so-called “hockey-stick” shape of the u☆−U relationship, which consists of a slow increase of u☆ with increasing wind speed for U<Utr and a more rapid almost linear increase of u☆ for U>Utr, where Utr is the wind speed of transition between the two regimes. Such a relationship is most pronounced at the highest observational levels, namely at 9 and 14 m, and is also sharper when the air-surface temperature difference exceeds its average values for stable conditions. It is shown that the Monin–Obukhov similarity theory (MOST) reproduces the observed u☆−U relationship rather well. This suggests that at least for the SHEBA dataset, there is no contradiction between MOST and the “hockey-stick” shape of the u☆−U relationship. However, the SHEBA data, as well as the single-column simulations show that for cases with strong stability, u☆ significantly decreases with height due to the shallowness of the ABL. It was shown that when u☆ was assumed independent of height, the value of the normalized drag coefficient, i.e., of the so-called stability correction function for momentum, calculated using observations at a certain level, can be significantly underestimated. To overcome this, the decrease of u☆ with height was taken into account in the framework of MOST using local scaling instead of the scaling with surface fluxes. Using such an extended MOST brought the estimates of the normalized drag coefficient closer to the Businger–Dyer relation.