Historicism and constructionism: rival ideas of historical change

Simon ZB. Historicism and constructionism: rival ideas of historical change. History of European Ideas. 2019;45(8):1171-1190.A seemingly unitary appeal to history might evoke today two incompatible operations of historicization that yield contradictory results. This article attempts to understand two co-existing senses of historicity as conflicting ideas of historical change and rival practices of temporal comparison: historicism and constructionism. At their respective births, both claimed to make sense of the world and ourselves as changing over time. Historicism, dominating nineteenth-century Western thought and overseeing the professionalization of historical studies, advocated an understanding of the present condition of the human world as developing out of past conditions. Constructionism, dominating the second half of the twentieth century, understood the present condition as the recent invention of certain ‘historical’ environments, without prior existence. As competing ideas of historical change, they both entail a comparison between past and present conditions of their investigated subjects, but their practices of temporal comparison are irreconcilable and represent two distinct ways of historicization

Timeframe of socket corticalization after tooth extraction : A retrospective radiographic study

Background The formation of a hard-tissue bridge covering the tooth extraction socket is termed corticalization. In dogs this process takes >60d, however, this process has hardly been investigated in humans. Recent reports have indicated increased primary implant stability and reduced bone strain after immediate implant loading in the presence of a (thick) cortical layer, thus, knowledge of the timeframe between tooth extraction and hard-tissue bridging of the extraction socket appears clinically relevant in some situations. Aim/Hypothesis To determine the timeframe between tooth extraction and radiographically detectable corticalization of the socket in humans and to evaluate the possible impact of various factors on this process, e.g., history of periodontitis, smoking status, systemic disease, medications, etc. Material and Methods Two-hundred-fifty patients with a CT scan μ 8804, 36 months after tooth extraction and without any manipulation at the extraction site were included. Three orthoradial multiplanar reconstruction slices per extraction socket were scored, by a single calibrated examiner, regarding the degree of corticalization as: (a) healed, i.e., complete/continuous corticalization of the socket entrance, or (b) non-healed. Thereafter, each extraction socket was classified as (1) non-corticalized, i.e., all 3 slices classified as non-healed, (2) partially corticalized, i.e., 1 or 2 slices classified as non-healed, or (3) corticalized, i.e., all 3 slices classified as healed (Figure 1). The possible effect of several independent parameters, i.e., age, gender, timeframe between tooth extraction and CT scan, tooth type, periodontal status, gap dimension, smoking status, presence of any systemic disease, and medication intake, on the corticalization status was statistically evaluated. Results Three to 6 months after tooth extraction, 27% of the sockets were judged as non-corticalized, and 53% were judged as partially corticalized. After 9 to 12 months, >80% of the sockets were corticalized, but some non-corticalized sockets were detected up to 15 months post-extraction (Figure 2). Each additional month after tooth extraction contributed significantly to higher likelihood of a corticalized socket (OR 1.645, 95% CIs 1.471–1.841, P < 0.001). Periodontal attachment loss of μ 8805, 75% significantly prolonged corticalization time, i.e., teeth with <75% attachment loss were judged more often as corticalized (OR 1.984, 95% CIs 1.011–3.896, P = 0.047). No other independent variable had a significant effect on corticalization status. Conclusions and Clinical Implications Three to 6 months after tooth extraction one out of 4 sockets was still completely non corticalized, and only 9 to 12 months after tooth extraction complete corticalization was observed in about 80% of the sockets. The results, indicating a considerably long timeframe until corticalization of extraction sockets, imply that in cases where immediate loading requiring high primary implant stability is considered, waiting μ 8805,9 months post-extraction appears advisable

On the Structure and Origin of Major Glaciation Cycles .2. the 100,000-year Cycle

Climate over the past million years has been dominated by glaciation cycles with periods near 23,000, 41,000, and 100,000 years. In a linear version of the Milankovitch theory, the two shorter cycles can be explained as responses to insolation cycles driven by precession and obliquity. But the 100,000-year radiation cycle (arising from eccentricity variation) is much too small in amplitude and too late in phase to produce the corresponding climate cycle by direct forcing. We present phase observations showing that the geographic progression of local responses over the 100,000-year cycle is similar to the progression in the other two cycles, implying that a similar set of internal climatic mechanisms operates in all three. But the phase sequence in the 100,000-year cycle requires a source of climatic inertia having a time constant (similar to 15,000 years) much larger than the other cycles (similar to 5,000 years). Our conceptual model identifies massive northern hemisphere ice sheets as this larger inertial source. When these ice sheets, forced by precession and obliquity, exceed a critical size, they cease responding as linear Milankovitch slaves and drive atmospheric and oceanic responses that mimic the externally forced responses. In our model, the coupled system acts as a nonlinear amplifier that is particularly sensitive to eccentricity-driven modulations in the 23,000-year sea level cycle. During an interval when sea level is forced upward from a major low stand by a Milankovitch response acting either alone or in combination with an internally driven, higher-frequency process, ice sheets grounded on continental shelves become unstable, mass wasting accelerates, and the resulting deglaciation sets the phase of one wave in the train of 100,000-year oscillations. Whether a glacier or ice sheet influences the climate depends very much on the scale....The interesting aspect is that an effect on the local climate can still make an ice mass grow larger and larger, thereby gradually increasing its radius of influence

Millennial-scale versus long-term dynamics in the surface and subsurface of the western North Atlantic Subtropical Gyre during Marine Isotope Stage 5

Subtropical Gyres are an important constituent of the ocean–atmosphere system due to their capacity to store vast amounts of warm and saline waters. Here we decipher the sensitivity of the (sub)surface North Atlantic Subtropical Gyre with respect to orbital and millennial scale climate variability between ~ 140 and 70 ka, Marine Isotope Stage (MIS) 5. Using (isotope) geochemical proxy data from surface and thermocline dwelling foraminifers from Blake Ridge off the west coast of North America (ODP Site 1058) we show that the oceanographic development at subsurface (thermocline) level is substantially different from the surface ocean. Most notably, surface temperatures and salinities peak during the penultimate deglaciation (Termination II) and early MIS 5e, implying that subtropical surface ocean heat and salt accumulation might have resulted from a sluggish northward heat transport. In contrast, maximum thermocline temperatures are reached during late MIS 5e when surface temperatures are already declining. We argue that the subsurface warming originated from intensified Ekman downwelling in the Subtropical Gyre due to enhanced wind stress. During MIS 5a-d a tight interplay of the subtropical upper ocean hydrography to high latitude millennial-scale cold events can be observed. At Blake Ridge, the most pronounced of these high latitude cold events are related to surface warming and salt accumulation in the (sub)surface. Similar to Termination II, heat accumulated in the Subtropical Gyre probably due to a reduced Atlantic Meridional Overturning Circulation. Additionally, a southward shift and intensification of the subtropical wind belts lead to a decrease of on-site precipitation and enhanced evaporation, coupled to intensified gyre circulation. Subsequently, the northward advection of this warm and saline water likely contributed to the fast resumption of the overturning circulation at the end of these high latitude cold events

Permafrost in Svalbard: a review of research history, climatic background and engineering challenges

This paper reviews permafrost in High Arctic Svalbard, including past and current research, climatic background, how permafrost is affected by climatic change, typical permafrost landforms and how changes in Svalbard permafrost may impact natural and human systems. Information on active layer dynamics, permafrost and ground ice characteristics and selected periglacial features is summarized from the recent literature and from unpublished data by the authors. Permafrost thickness ranges from less than 100 m near the coasts to more than 500 m in the highlands. Ground ice is present as rock glaciers, as ice-cored moraines, buried glacial ice, and in pingos and ice wedges in major valleys. Engineering problems of thaw-settlement and frost-heave are described, and the implications for road design and construction in Svalbard permafrost areas are discussed