Simultaneous Bedside Assessment of Global Cerebral Blood Flow and Effective Cerebral Perfusion Pressure in Patients with Intracranial Hypertension

Background: We examined a bedside technique transcerebral double-indicator dilution (TCID) for global cerebral blood flow (CBF) as well as the concept of effective cerebral perfusion pressure (CPPeff) during different treatment options for intracranial hypertension, and compared global CBF and CPPeff with simultaneously obtained conventional parameters. Methods: Twenty-six patients developing intracranial hypertension in the course of traumatic brain injury or subarachnoid hemorrhage were prospectively analyzed using a combined assessment during elevated ventilation (n=15) or osmotherapy (hypertonic saline or mannitol). For calculation of global CBF, injections of ice-cold indocyanine green boluses were performed and temperature and dye concentration changes were monitored in the thoracic aorta and the jugular bulb. CBF was then calculated according to the mean transit time principle. Estimation of CCP, the arterial pressure at which cerebral blood flow becomes zero, was performed by synchronized registration of corresponding values of blood flow velocity in the middle cerebral artery and arterial pressure and extrapolation to zero-flow velocity. CPPeff was calculated as mean arterial pressure minus critical closing pressure (CPPeff=MAPc−CCP). Results: Elevated ventilation causes a decrease in both ICP (P<0.001) and CBF (P<0.001). While CPPconv increased (P<0.001), CPPeff decreased during this observation (P=0.002). Administration of osmotherapeutic agents resulted in a decrease of ICP (P<0.001) and a temporary increase of CBF (P=0.052). CPPconv and CPPeff showed no striking difference under osmotherapy. Conclusion: TCID allows repeated measurements of global CBF at the bedside. Elevated ventilation lowered and osmotherapy temporarily raised global CBF. In situations of increased vasotonus, CPPeff is a better indicator of blood flow changes than conventional CP

Role of food web interactions in promoting resilience to nutrient enrichment in a brackish water eelgrass (Zostera marina) ecosystem

Understanding the ecological interactions that enhance the resilience of threatened ecosystems is essential in assuring their conservation and restoration. Top-down trophic interactions can increase resilience to bottom-up nutrient enrichment, however, as many seagrass ecosystems are threatened by both eutrophication and trophic modifications, understanding how these processes interact is important. Using a combination of approaches, we explored how bottom-up and top-down processes, acting individually or in conjunction, can affect eelgrass meadows and associated communities in the northern Baltic Sea. Field surveys along with fish diet and stable isotope analyses revealed that the eelgrass trophic network included two main top predatory fish species, each of which feeds on a separate group of invertebrate mesograzers (crustaceans or gastropods). Mesograzer abundance in the study area was high, and capable of mitigating the effects of increased algal biomass that resulted from experimental nutrient enrichment in the field. When crustacean mesograzers were experimentally excluded, gastropod mesograzers were able to compensate and limit the effects of nutrient enrichment on eelgrass biomass and growth. Our results suggest that top-down processes (i.e., suppression of algae by different mesograzer groups) may ensure eelgrass resilience to nutrient enrichment in the northern Baltic Sea, and the existence of multiple trophic pathways can provide additional resilience in the face of trophic modifications. However, the future resilience of these meadows is likely threatened by additional local stressors and global environmental change. Understanding the trophic links and interactions that ensure resilience is essential for managing and conserving these important ecosystems and the services they provide

A left-handed simplicial action for euclidean general relativity

An action for simplicial euclidean general relativity involving only left-handed fields is presented. The simplicial theory is shown to converge to continuum general relativity in the Plebanski formulation as the simplicial complex is refined. This contrasts with the Regge model for which Miller and Brewin have shown that the full field equations are much more restrictive than Einstein's in the continuum limit. The action and field equations of the proposed model are also significantly simpler then those of the Regge model when written directly in terms of their fundamental variables. An entirely analogous hypercubic lattice theory, which approximates Plebanski's form of general relativity is also presented.Comment: Version 3. Adds current home address + slight corrections to references of version 2. Version 2 = substantially clarified form of version 1. 29 pages, 4 figures, Latex, uses psfig.sty to insert postscript figures. psfig.sty included in mailing, also available from this archiv

Temperature correction to the Casimir force in cryogenic range and anomalous skin effect

Temperature correction to the Casimir force is considered for real metals at low temperatures. With the temperature decrease the mean free path for electrons becomes larger than the field penetration depth. In this condition description of metals with the impedance of anomalous skin effect is shown to be more appropriate than with the permittivity. The effect is crucial for the temperature correction. It is demonstrated that in the zero frequency limit the reflection coefficients should coincide with those of ideal metal if we demand the entropy to be zero at T=0. All the other prescriptions discussed in the literature for the $n=0$ term in the Lifshitz formula give negative entropy. It is shown that the temperature correction in the region of anomalous skin effect is not suppressed as it happens in the plasma model. This correction will be important in the future cryogenic measurements of the Casimir force.Comment: 12 pages, 2 figures, to be published in Phys. Rev.

Personalized drug sensitivity screening for bladder cancer using conditionally reprogrammed patient-derived cells

Many patients with muscle-invasive bladder cancer (BC) are either ineligible for or do not benefit from cisplatin-based chemotherapy, and there is an unmet need to estimate individuals’ drug sensitivities. We investigated the suitability of conditionally reprogrammed (CR) cells for the characterization of BC properties and their feasibility for personalized drug sensitivity screening. The CR cultures were established from six BC tumors with varying histology and stage. Four cultures were successfully propagated for genomic, transcriptomic, and protein expression profiling and compared to the parental tumors. Two out of four CR cultures (urothelial carcinoma and small cell neuroendocrine carcinoma [SmCC]) corresponded well to their parental tumors and underwent drug sensitivity screening to identify novel drugs for the respective tumors. Both cultures were sensitive to standard BC chemotherapy agents (eg cisplatin and gemcitabine) and to conventional drugs such as taxanes and inhibitors of topoisomerase and proteasome. The SmCC cells were also sensitive to statins (eg, atorvastatin and pitavastatin). In summary, after confirming their representativeness and origin, we conclude that CR cells are a feasible platform for personalized drug sensitivity testing and might thus add to the approaches used to personalize BC treatment strategies

Effect of excess charge carriers and fluid medium on the magnitude and the sign of the Casimir-Lifshitz torqueP. Thiyam

Last year, we reported a perturbative theory of the Casimir-Lifshitz torque between planar biaxially anisotropic materials in the retarded limit [Phys. Rev. Lett. {\bf 120}, 131601 (2018)], which is applied here to study the change of sign and magnitude of the torque with separation distance in biaxial black phosphorus having excess charge carriers. The study is carried out both in vacuum as well as in a background fluid medium. The presence of extra charge carriers and that of an intervening fluid medium are both found to promote enhancement of the magnitude of the torque between identical slabs. The degree of enhancement of the magnitude of torque increases not only with an increased carrier concentration but also with separation distance. In the non-identical case when different planes of anisotropic black phosphorus face each other, owing to the non-monotonic characteristic of the sign-reversal effect of the torque, the enhancement by carrier addition and intervening medium also becomes non-monotonic with distance. In the presence of a background medium, the non-monotonic degree of enhancement of the torque with distance is observed even between identical slabs