Optimal Design of Heat Exchangers to Enhance Thermal Performance

Heat transfer is a key aspect of devices and industrial processes for maintaining their functionality and achieving better product quality. Heat exchangers of different types and sizes are used to transfer heat between a source and a working fluid to maintain the desirable working temperatures. Due to the space requirements of devices, there is a need for efficient heat exchangers with less size and less weight. Gyroid structure is a type of Triply Periodic Minimal Surface structures that define an internal volume that maximizes surface area and strength while minimizing mass. The hypothesis is that gyroid structures are useful in heat exchanger design, as they can optimize heat transfer to be more efficient, compared to traditional heat exchanger designs. A gyroid structured heat exchanger was designed, 3D printed, and compared to a commercial plate heat exchanger. Using different water flow rates, temperatures at the hot and cold inlets/outlets were measured using thermocouples and PicoLog until they reached steady state and calculated heat transfer rate and efficiency. It is found that heat transfer rate linearly increases with flow rate and that the heat transfer rate for the commercial heat exchanger is about twice the heat transfer rate for the gyroid one. A gyroid heat exchanger with the same surface area as the commercial one is likely to have a much larger heat transfer rate. Additional measurements, such as pressure drop and internal volume, should be taken to properly compare different heat exchangers, while minimizing heat loss and uncertainty in data

Histopathological analysis of spontaneous large necrosis of adrenal pheochromocytoma manifested as acute attacks of alternating hypertension and hypotension: a case report

BACKGROUND: Pheochromocytomas are rare catecholamine-producing neuroendocrine tumors. Hypertension secondary to pheochromocytoma is often paroxysmal, and patients occasionally present with sudden attacks of alternating hypertension and hypotension. Spontaneous, extensive necrosis within the tumor that is associated with catecholamine crisis is an infrequent complication of adrenal pheochromocytoma, but its pathogenesis remains unclear. CASE PRESENTATION: A 69-year-old Japanese man developed acute-onset episodic headaches, palpitations, and chest pains. During the episodes, both marked fluctuations in blood pressure (ranging from 40/25 to 300/160 mmHg) and high plasma levels of catecholamines were found simultaneously. Radiological findings indicated a 4-cm left adrenal pheochromocytoma. These episodic symptoms disappeared within 2 weeks with normalization of plasma catecholamine levels. Two months later, the patient underwent adrenalectomy. Microscopic examinations revealed pheocromocytoma with a large central area of coagulative necrosis. The necrotic material was immunohistochemically positive for chromogranin A. Granulation tissue was adjacent to the necrotic area, accompanied by numerous hemosiderin-laden macrophages and histiocytes with vascular proliferation. Viable tumor cells, detected along the periphery of the tumor, demonstrated pyknosis, and the Ki-67 labeling index was 2 % in the hot spot. No embolus or thrombus formation was found in the resected specimen harboring the whole tumor. The Pheochromocytoma of the Adrenal gland Scaled Score was 2 out of 20. The patient’s postoperative course was unremarkable for > 7 years. CONCLUSIONS: Presumed causal factors for the extensive necrosis of adrenal pheochromocytoma in previously reported cases include hemorrhage into the tumor, hypotension induced by a phentolamine administration, embolic infarction, high intracapsular pressure due to malignant growth of the tumor, and catecholamine-induced vasoconstriction. In the present case, histopathological and clinical findings suggest that under conditions of chronic ischemia due to catecholamine-induced vasoconstriction, an acute infarction occurred after sudden attacks of alternating hypertension and hypotension. Over the subsequent 2 weeks, repetitive massive release of catecholamines from the infarcts into circulation likely accelerated infarction progression by causing repeated attacks of alternating hypertension and hypotension and resulted in the large necrosis. This case highlights the need for physicians to consider acute spontaneous tumor infarction accompanying episodic catecholamine crisis as a rare but severe complication of pheochromocytoma

RETRACTED: The Chromatin-Remodeling Complex WINAC Targets a Nuclear Receptor to Promoters and Is Impaired in Williams Syndrome

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).This article has been retracted at the request of the Authors.Our paper reported that a chromatin-remodeling complex, WINAC, recruited the unliganded vitamin D receptor to promoters in cooperation with the transcription factor implicated in Williams syndrome, WSTF. The findings provided insights into the coordination between chromatin remodelers and sequence-specific transcription factors and pointed to a role of chromatin remodeling defects in Williams syndrome. We recently identified errors affecting several figure panels where original data were processed inappropriately such that the figure panels do not accurately report the original data. We believe that the most responsible course of action is to retract the paper. We sincerely apologize to the scientific community for any inconvenience that this might cause. The first author, H.K., declined to sign the retraction notice

Droplet Impact, Part 1: Controlling Skirting Velocity

Droplet skirting occurs when a fluid droplet rolls over a bath of the same fluid without merging. To achieve skirting, we introduced a ~0.6 mm-diameter droplet of 1 cSt silicone oil into a bath of the same fluid by bouncing it off an angled glass slide coated with 100,000 cSt silicone oil. Our work suggests that initial skirting velocity increases as a function of slide angle and, to a lesser degree, droplet generator height. Furthermore, we conclude that the droplet lifetimes (initiation of skirting until rupture) and corresponding values (rate of decay of motion) appear consistent with theoretical predictions for such droplets based on previous research (which did not address \u3e0.75 mm-diameter droplets

Droplet Impact, Part 2: Engineering a Droplet Generator

Prior droplet impact research at DePauw used a syringe to pump fluid through a tube to create a droplet. This method generated ~2.5mm diameter droplets with secondary satellite droplets that formed during pinch-off and influenced rupture upon collision with the main droplet. Furthermore, the large diameter caused the droplet to experience significant oscillation as it fell, making it difficult to control impact shape without changing impact velocity. Part of this summer’s research focused on adapting preexisting designs for droplet generators to build our own version that creates small, consistent droplets without interference from satellite droplets or jets (which form at high speeds/large diameters)

MEMS 411: 3D Clay Printer

The Washington University School of Architecture has a class called Digital Ceramics, that utilizes a 3D Printer that prints clay instead of plastic filament. Students use this device to make art projects. As interesting as this device is, it isn’t without problems. Our team decided to tackle some of the problems involved which we recognized to be: long set-up and tear-down times, and unsuccessful prints due to nozzle falling out

Temperature dependence of aragonite and calcite skeleton formation by a scleractinian coral in low mMg/Ca seawater

Temperature-dependent aragonite and calcite formation by scleractinian corals were examined in low molar (m) Mg/Ca seawater, the experimental conditions replicating the fluctuating mMg/Ca levels prevailing throughout the Phanerozoic Eon. Incubation and skeletal growth monitoring of juveniles of the scleractinian coral Acropora solitaryensis for 4 months from the planula stage, in seawater with mMg/Ca ratios of 5.2, 1.0, and 0.5, and temperatures of 19–28 °C, indicated that polymorphism of present-day scleractinian corals in low mMg/Ca seawater is also influenced by seawater temperature. However, corals produced more aragonite than formed in inorganic CaCO3 precipitation experiments under the same conditions, except at 19 °C. Although the aragonite content reflected the results of the latter (abiotic) experiments at 19 °C, it is suggested that aragonitic scleractinian corals controlled skeletal formation biologically under low mMg/Ca conditions at higher temperature, growth rates being faster at 25 °C and slower at 19 °C for all mMg/Ca ratios. Compared with growth rates under the present-day-equivalent seawater Mg/Ca level of 5.2, juvenile growth decreased by 62.8% ± 14.7% and 56.7% ± 6.7% under mMg/Ca levels of 1.0 and 0.5, respectively; the results suggest that growth of aragonitic scleractinian corals is suppressed throughout varying seasonal temperatures under low mMg/Ca conditions. This supports previous findings from variable temperature perspectives that scleractinian corals grow more slowly in low mMg/Ca (Cretaceous) seawater, interpreted as a possible explanation for the hiatus in scleractinian reef building in the Cretaceous Period

Transcriptomic response in <i>Acropora muricata</i> under acute temperature stress follows preconditioned seasonal temperature fluctuations

Objective: Global climate change has resulted in the decline of health and condition of various coral reefs worldwide. Here, we describe expression profiles of Acropora muricata collected during opposing seasons in Otsuki, Kochi, Japan to define the capacity of corals to cope with changing environmental conditions. Coral communities in Otsuki experience large temperature fluctuations between the winter (~ 16 °C) and summer (~ 27 °C). Results: Coral nubbins that were collected in the summer showed no change in photochemical efficiency when exposed to thermal or cold stress, while winter samples showed a decrease in photochemical health when subjected to thermal stress. Under cold stress, corals that were collected in the summer showed an up-regulation of actin-related protein and serine/threonine protein kinase, while corals collected during the winter did not show any cellular stress. On the other hand, under thermal stress, the most notable change was the up-regulation of phosphoenolpyruvate carboxykinase in corals that were collected during the winter season. Our observations in the differential genes expressed under temperature-derived stress suggest that A. muricata from Kochi may maintain physiological resilience due to the frequently encountered environmental stress, and this may play a role in the coral’s thermal tolerance.</p

All-In-One: Advanced preparation of Human Parenchymal and Non-Parenchymal Liver Cells

BACKGROUND & AIMS: Liver cells are key players in innate immunity. Thus, studying primary isolated liver cells is necessary for determining their role in liver physiology and pathophysiology. In particular, the quantity and quality of isolated cells are crucial to their function. Our aim was to isolate a large quantity of high-quality human parenchymal and non-parenchymal cells from a single liver specimen. METHODS: Hepatocytes, Kupffer cells, liver sinusoidal endothelial cells, and stellate cells were isolated from liver tissues by collagenase perfusion in combination with low-speed centrifugation, density gradient centrifugation, and magnetic-activated cell sorting. The purity and functionality of cultured cell populations were controlled by determining their morphology, discriminative cell marker expression, and functional activity. RESULTS: Cell preparation yielded the following cell counts per gram of liver tissue: 2.0+/-0.4x107 hepatocytes, 1.8+/-0.5x106 Kupffer cells, 4.3+/-1.9x105 liver sinusoidal endothelial cells, and 3.2+/-0.5x105 stellate cells. Hepatocytes were identified by albumin (95.5+/-1.7%) and exhibited time-dependent activity of cytochrome P450 enzymes. Kupffer cells expressed CD68 (94.5+/-1.2%) and exhibited phagocytic activity, as determined with 1mum latex beads. Endothelial cells were CD146+ (97.8+/-1.1%) and exhibited efficient uptake of acetylated low-density lipoprotein. Hepatic stellate cells were identified by the expression of alpha-smooth muscle actin (97.1+/-1.5%). These cells further exhibited retinol (vitamin A)-mediated autofluorescence. CONCLUSIONS: Our isolation procedure for primary parenchymal and non-parenchymal liver cells resulted in cell populations of high purity and quality, with retained physiological functionality in vitro. Thus, this system may provide a valuable tool for determining liver function and disease

Rapid Detection of Botulinum Neurotoxins—A Review

A toxin is a poisonous substance produced within living cells or organisms. One of the most potent groups of toxins currently known are the Botulinum Neurotoxins (BoNTs). These are so deadly that as little as 62 ng could kill an average human; to put this into context that is approximately 200,000 × less than the weight of a grain of sand. The extreme toxicity of BoNTs leads to the need for methods of determining their concentration at very low levels of sensitivity. Currently the mouse bioassay is the most widely used detection method monitoring the activity of the toxin; however, this assay is not only lengthy, it also has both cost and ethical issues due to the use of live animals. This review focuses on detection methods both existing and emerging that remove the need for the use of animals and will look at three areas; speed of detection, sensitivity of detection and finally cost. The assays will have wide reaching interest, ranging from the pharmaceutical/clinical industry for production quality management or as a point of care sensor in suspected cases of botulism, the food industry as a quality control measure, to the military, detecting BoNT that has been potentially used as a bio warfare agent