Strong interlayer coupling in two-dimensional PbSe with high thermoelectric performance.

It was generally believed that weak van der Waals interactions exist between neighboring layers in the two-dimensional group-IV chalcogenides. Using PbSe as a prototypal example, we find additional strong coupling between the Pb-Pb layers, as evidenced by detailed analysis of the differential charge density plot. The coupling is covalent-like and can be fine-tuned to obviously reduce the phonon thermal conductivity but slightly change the electronic transport of PbSe layer. As a consequence, a maximumZTvalue of 2.5 can be realized at 900 K for thep-type system. Our work also offers an effective and feasible design strategy to enhance the thermoelectric performance of similar layered structures.

Surprisingly good thermoelectric performance of a black phosphorus/blue phosphorus van der Waals heterostructure.

Thermoelectric properties of a black phosphorus/blue phosphorus van der Waals heterostructure are investigated by using first-principles calculations and Boltzmann transport theory for both electrons and phonons. It is found that the heterostructure is both energetically and kinetically stable even at higher temperature. Compared with those of the constituent black and blue phosphorus monolayers, the thermoelectric performance of the heterostructure is significantly enhanced due to sharply decreased thermal conductivity caused by the presence of van der Waals interactions, as well as obviously reduced band gaps and multi-valley structures resulting from type-II band alignment. As a consequence, the room temperature ZT value can reach 1.6, which is much higher than those of the components. Furthermore, we obtain ZT over 2.0 in a wide temperature range from 400 to 800 K, and a maximum ZT of ∼3.2 can be realized at 700 K, which is surprisingly good for systems consisting of light elements only.

High thermoelectric performance of half-Heusler compound BiBaK with intrinsically low lattice thermal conductivity.

Half-Heusler compounds usually exhibit relatively higher lattice thermal conductivity that is undesirable for thermoelectric applications. Here we demonstrate by first-principles calculations and Boltzmann transport theory that the BiBaK system is an exception, which has rather low thermal conductivity as evidenced by very small phonon group velocity and relaxation time. Detailed analysis indicates that the heavy Bi and Ba atoms form a cage-like structure, inside which the light K atom rattles with larger atomic displacement parameters. In combination with its good electronic transport properties, the BiBaK shows a maximum n-type ZT value of 1.9 at 900 K, which outperforms most half-Heusler thermoelectric materials.

Tissue lipopolysaccharide-binding protein expression in rats after thermal injury: potential role of TNF-alpha.

Recent studies have suggested that levels of lipopolysaccharide-binding protein (LBP) might play a harmful role by up-regulating the host's sensitivity to endotoxin. Our previous studies demonstrated that local endotoxin could up-regulate LBP expression after acute insults, however, the definite molecular mechanisms downstream of endotoxin action remain unclear. This study investigates whether tumor necrosis factor (TNF-alpha) might be responsible for the LBP formation during endogenous endotoxemia postburn. Wistar rats were anesthetized, and a 35% TBSA full-thickness burn was created. Animals were randomly divided into normal control, thermal injury and anti-TNF-alpha mAb treatment group. A significant elevation of plasma endotoxin concentration was observed after acute insults. TNF-alpha levels in plasma also rapidly increased after thermal injury. Meanwhile, LBP mRNA expression markedly increased in liver, lungs, kidneys and intestine postburn. There was no detectable TNF-alpha in the plasma of anti-TNF-alpha mAb treated animals. Treatment with anti-TNF-alpha mAb also resulted in significantly lower concentrations of LBP mRNA in local tissues. Additionally, several organ function parameter levels in plasma significantly decreased in treatment group. These results demonstrated that an increase of plasma TNF-alpha levels caused by burns might be associated with a marked elevation of tissue LBP mRNA expression, which could contribute to the development of multiple organ damage.

Anisodamine restores bowel circulation in burn shock.

In a group of eight burn patients with a mean of 65.3 +/- 17.4 per cent TBSA burn injury (range 50-90 per cent TBSA), accompanied by a mean of 43.5 +/- 18.9 per cent TBSA full-thickness injury, it was shown that the evidence of global hypovolaemia had disappeared at 12 h after the injury following aggressive fluid resuscitation, while there was still a subnormal pHi of stomach at 48 h. As a prolonged period of inadequacy of oxygen delivery to the intestine might result in impairment of the intestinal mucosal barrier function, and then endogenous endotoxaemia might ensue, it seems to be important to correct intestinal hypoxia as early as possible. Since the inadequate perfusion to the gut wall is due to selective vasoconstriction of the mesenteric vasculature, logic dictates that the use of a vasodilator is in order. Anisodamine, an anticholinergic drug, was then given in six burn patients with comparable burn size and amount of fluid replenishment with the eight patients in the control group. It was clearly demonstrated that gastric pHi returned to normal before 48 h after injury. Plasma endotoxin and TNF contents were measured, and they were significantly lower than control values after 72 h. In conclusion, it is believed that anisodamine might be a valuable adjunct to the resuscitation regime of burn shock, and, therefore, a promising drug to abate endogenous endotoxaemia subsequent to splanchnic vasoconstriction due to hypovolaemia. The shortcomings of the drug were a mild abdominal distention and tachycardia after its administration.

Extensive wound excision in the acute shock stage in patients with major burns.

In order to reduce excessive plasma loss, to alleviate the effects of devitalized tissues on the body, and to shorten the time in hospital, we attempted to perform extensive escharectomy during the shock period in extensively burned patients. Group A consisted of 21 patients, aged 9-45 years, with a mean total burn area of 63.2 +/- 18.1 per cent TBSA, and full-thickness injury involving 35.9 +/- 19.6 per cent TBSA. The first escharectomy was performed at 24.1 +/- 13.9 h postburn. The excision area averaged 32.3 +/- 6.7 per cent TBSA (range 24-96 per cent). In 15 patients a Swan-Ganz catheter was introduced to monitor haemodynamic changes. It was found that RAP, PAP, PAWP, ABP, HR, CO and CI were all stable during and after the operation. Group B consisted of 29 patients, and escharectomy was begun 4-5 days postburn. The mean healing time of the patients in group A was 33.1 days, which was shorter than that in group B (40.1 days). The period of haemoconcentration was shorter in group A and the amount of blood required during the first 2 weeks was almost 700 ml less in group A. There were fewer visceral complications in group A and smaller amounts of antibiotics were required in this group. The authors believe that escharectomy during the shock stage is feasible.

Metabolic abnormalities of mitochondrial redox potential in postburn multiple system organ failure.

Forty-five burn patients underwent sequential assays for plasma acetoacetate and beta-hydroxybutyrate concentrations as well as plasma amino acid levels. Those patients who went on to develop multiple system organ failure were noted to have a decrease in their acetoacetate concentration with time, whereas there was no change in those patients who failed to develop multiple system organ failure. The plasma concentration of beta-hydroxybutyrate was not altered by multiple system organ failure. In addition, the plasma acetoacetate/beta-hydroxybutyrate ratio was found to be directly related to the plasma concentration of branched chain amino acids and inversely related to the concentration of aromatic amino acids.

Study of permanent artificial tendon.

The aim of the present study was to develop a porous, silastic tube with filmy wall acting as permanent artificial tendon. Twelve mongrel dogs were used. Peronaeus longus and Tibialis anticus were exposed respectively, divided in two places and sutured in situ. They were covered by the above-mentioned silastic tube. One dog each was sacrificed after 1, 2, 4, 6, 8, 10, 12, 16, 20 and 24 weeks, and 11 months; specimens were removed. Each preparation was studied as follows: gross observation and light microscopy for tendon preparation; transmission electron microscopy, scanning electron microscopy and phase microscopy for the pseudosheath. Our study showed that healing of tendon was mainly extrinsic mechanism and that the pseudosheath formed by silastic tube can prevent the adhesion of the surrounding tissue; therefore, use of the artificial tendon including a tendongraft coated with a silastic tube in reconstruction of flexor digital tendon in the hand is procedure feasible. But what the appropriate porous diameter and porous distance are, must be studied further. Tendon gliding mainly depends upon the gliding plane between the composite body of the tendon and the loose connective tissues around it.

Surgery in China today.

The fusion of traditional and modern concepts is a unique feature of medical practice in China. Since 1949, there have been considerable achievements particularly in the fields of burns, surgery of the liver, pancreas and the heart, and in microsurgery and limb reimplantation. Surgical skills are now distributed through medical units outside the large cities, and at the grass-roots level, making them available to peasants. Research facilities remain limited and are responsible for the slow and uneven progress in surgery but the new China will spare no efforts to fill the gap and learn from all developed countries.