[Efficacy and outcomes of shunt surgery for secondary hydrocephalus].

Records of secondary hydrocephalus patients undergoing shunt surgery in the Department of Neurosurgery of Peking Union Medical College Hospital from September 2012 to April 2022 and their clinical characteristics and outcomes were retrospectively reviewed and analyzed. Among 121 patients who received first time shunt placement, the most common causes of secondary hydrocephalus were brain hemorrhage (55, 45.5%) and trauma (35, 28.9%). Cognition decline (106, 87.6%), abnormal gait (50, 41.3%) and incontinence (40, 33.1%) were the most prevalent manifestations. Postoperative central nervous system infection (4, 3.3%), shunt obstruction (3, 2.5%) and subdural hematoma/effusion (4, 3.3%) were the most frequent neurological complications. Overall incidence of postoperative complications was 9% (11 cases) in the current cohort. And 50.5% (54/107) of the patients receiving shunting achieved a Glasgow outcome scale (GOS) score of at least 4. Shunt surgery is preferred for secondary hydrocephalus, especially for secondary normal pressure hydrocephalus. Moreover, it is recommended to complete cranioplasty in staged operation or one-stage operation for the patients with decompressive craniectomy.

[Relationship between white matter lesions and theresponse of cerebral spinal fluid tap test and clinical features in the patients with idiopathic normal pressure hydrocephalus].

Objective: To explore the relationship between white matter lesions and clinical features and response of cerebral spinal fluid (CSF) tap test in patients with idiopathic normal pressure hydrocephalus(iNPH). Methods: Possible iNPH patients were enrolled from outpatients and inpatients in Peking Union Medical College Hospital between 2014 and 2019. All patients underwent detailed neuropsychological and walking assessments, CSF tap test, as well as head magnetic resonance imaging. The Fazekas score of white matter lesions, the fractional anisotropy (FA)and mean diffusivity (MD) values of regions of interest by means ofdiffusion tensor imaging (DTI) were compared between CSF tap test positive and negative response groups. The correlation between DTI parameters and clinical characteristics was analyzed. Results: Forty-three patients (29 male and 14 female, age range: 52-79 years] wererecruited.Compared with the negative group, patients in the positive group tended to have higher Fazekas score of periventricular white matter(U=108.00, P=0.03), higher MD value of the region near anterior horn of left lateral ventricles[(1.14±0.27)×10-9mm2/s vs (0.85±0.08) ×10-9mm2/s, P=0.003], lower FA value of the region near anterior horn of the right lateral ventricles[(0.20±0.07)vs(0.27±0.09), P=0.058], and higher MD value near the posterior horn of right lateral ventricle [(1.17±0.34)×10-9mm2/s vs (0.95±0.01)×10-9mm2/s, P=0.003]. FA and MD were significantly correlated with motor function, cognitive and functional scores, and iNPH grading scale (iNPHGS) scores(all P<0.05). Conclusions: The white matter lesions might be one of the pathogeneses of lNPH and apathological changewhich can be reversed by CSF drainage. More white matter lesions should not be the contraindication of CSF drainage surgery.

[Sacubitril/valsartan attenuates left ventricular remodeling and improve cardiac function by upregulating apelin/APJ pathway in rats with heart failure].

Objective: To investigate the effect and mechanism of sacubitril/valsartan on left ventricular remodeling and cardiac function in rats with heart failure. Methods: A total of 46 SPF-grade male Wistar rats weighed 300-350 g were acclimatized to the laboratory for 7 days. Rats were then divided into 4 groups: the heart failure group (n=12, intraperitoneal injection of adriamycin hydrochloride 2.5 mg/kg once a week for 6 consecutive weeks, establishing a model of heart failure); heart failure+sacubitril/valsartan group (treatment group, n=12, intragastric administration with sacubitril/valsartan 1 week before the first injection of adriamycin, at a dose of 60 mg·kg-1·d-1 for 7 weeks); heart failure+sacubitril/valsartan+APJ antagonist F13A group (F13A group, n=12, adriamycin and sacubitril/valsartan, intraperitoneal injection of 100 µg·kg-1·d-1 APJ antagonist F13A for 7 weeks) and control group (n=10, intraperitoneal injection of equal volume of normal saline). One week after the last injection of adriamycin or saline, transthoracic echocardiography was performed to detect the cardiac structure and function, and then the rats were executed, blood and left ventricular specimens were obtained for further analysis. Hematoxylin-eosin staining and Masson trichrome staining were performed to analyze the left ventricular pathological change and myocardial fibrosis. TUNEL staining was performed to detect cardiomyocyte apoptosis. mRNA expression of left ventricular myocardial apelin and APJ was detected by RT-qRCR. ELISA was performed to detect plasma apelin-12 concentration. The protein expression of left ventricular myocardial apelin and APJ was detected by Western blot. Results: Seven rats survived in the heart failure group, 10 in the treatment group, and 8 in the F13A group. Echocardiography showed that the left ventricular end-diastolic diameter (LVEDD) and the left ventricular end-systolic diameter (LVESD) were higher (both P<0.05), while the left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) were lower in the heart failure group than in the control group (both P<0.05). Compared with the heart failure group, rats in the treatment group were featured with lower LVEDD and LVESD (both P<0.05), higher LVEF and LVFS (both P<0.05), these beneficial effects were reversed in rats assigned to F13A group (all P<0.05 vs. treatment group). The results of HE staining showed that the cardiomyocytes of rats in the control group were arranged neatly and densely structured, the cardiomyocytes in the heart failure group were arranged in disorder, distorted and the gap between cells was increased, the cardiomyocytes in the treatment group were slightly neat and dense, and cardiomyocytes in the F13A group were featured similarly as the heart failure group. Masson staining showed that there were small amount of collagen fibers in the left ventricular myocardial interstitium of the control group, while left ventricular myocardial fibrosis was significantly increased, and collagen volume fraction (CVF) was significantly higher in the heart failure group than that of the control group (P<0.05). Compared with the heart failure group, the left ventricular myocardial fibrosis and the CVF were reduced in the treatment group (both P<0.05), these effects were reversed in the F13A group (all P<0.05 vs. treatment group). TUNEL staining showed that the apoptosis index (AI) of cardiomyocytes in rats was higher in the heart failure group compared with the control group (P<0.05), which was reduced in the treatment group (P<0.05 vs. heart failure group), this effect again was reversed in the F13A group (P<0.05 vs. treatment group). The results of RT-qPCR and Western blot showed that the mRNA and protein levels of apelin and APJ in left ventricular myocardial tissue of rats were downregulated in heart failure group (all P<0.05) compared with the control group. Compared with the heart failure group, the mRNA and protein levels of apelin and APJ were upregulated in the treatment group (all P<0.05), these effects were reversed in the F13A group (all P<0.05 vs. treatment group). ELISA test showed that the plasma apelin concentration of rats was lower in the heart failure group compared with the control group (P<0.05); compared with the heart failure group, the plasma apelin concentration of rats was higher in the treatment group (P<0.05), this effect was reversed in the F13A group (P<0.05 vs. treatment group). Conclusion: Sacubitril/valsartan can partially reverse left ventricular remodeling and improve cardiac function in rats with heart failure through modulating Apelin/APJ pathways.

[Effect of band ligation or combined with tissue adhesive in the treatment of gastroesophageal varices and portal vein blood flow situational changes].

42 cases with gastroesophageal varices were prospectively included. The groups were treated with endoscopic band ligation or combined with tissue adhesive. The results showed that the left gastric vein internal diameter, average blood flow velocity and blood flow volume after the treatment of band ligation combined with tissue adhesive were significantly lower than that of the treatment of band ligation alone, and the differences were statistically significant (P < 0.05). Spleen and portal vein internal diameter, blood flow and average velocity, the liver and spleen size, shear wave velocity and liver function grade of the two groups after treatment did not change significantly (P > 0.05). The effective rate of band ligation combined with tissue adhesive in the treatment of esophageal and gastric varices (66.67%, 52.38%) were higher than that of band ligation alone (42.85%, 23.81%) (P > 0.05), and the re-bleeding rate of the latter was higher (9.52% and 19.05%, P > 0.05). Hence, it is suggested that the combined therapy is safe and more effective, and has no apparent effect on liver function and portal hypertension.

[Efficacy of magnetic levitation elastic mandibular elevator in treatment of mild or moderate obstructive sleep apnea].

Objectives: To investigate the clinical efficacy of magnetic levitation elastic mandibular elevator (MLEME) in treatment of mild obstructive sleep apnea (OSA). Methods: Twenty one patients with mild or moderate OSA confirmed by polysomnographic (PSG) examination were recruited from the First Affiliated Hospital with Nanjing Medical University between June of 2016 and June of 2017. Their PSG parameters, daytime Epworth sleepiness score (ESS) were compared before and on treatment of MLEME. In addition, any side effects and discomfort were observed during MLEME treatment. Results: Comparison of parameters during and before MLEME treatment revealed a significant decrease (all P<0.05) in apnea hypopnea index [(9.3±6.2) vs (15.6±7.8)/h], arousal index [(6.2±3.4) vs (10.3±5.4)/h], percentage of sleep time with less than 90% oxygen saturation (3.9%±2.7% vs 9.8%±3.5%), daytime ESS (6.3±2.3 vs 11.2±2.8); but a remarkable increase (all P<0.05) in mean and minimal pulse oxygen saturation (97.2%±0.9% vs 94.7%±1.1% and 87.6%±2.8% vs 81.7%±4.6% respectively). All patients could tolerate MLEME treatment well with no complain of discomfort. Following wearing of MLEME, X-ray lateral film of head and neck revealed a significantly longer distance than that before MLEME treatment from tip of uvula to posterior pharyngeal wall [(11.9±1.8) vs (9.6±1.5) mm](P<0.05). Conclusions: MLEME could significantly improve sleep respiratory parameters and daytime sleepiness of OSA without side effects. Its long-term efficacy for OSA remains to be further explored.

[Advances in the study of gastroesophageal varices with portal vein thrombosis in liver cirrhosis].

Portal vein thrombosis (PVT) is one of the serious complications in the decompensated stage of liver cirrhosis, which is often accompanied by the aggravation of liver cirrhosis and other complications and in severe cases; it may induce gastroesophageal variceal hemorrhage and endanger the lives of patients. Furthermore, the most common complication in decompensated stage of cirrhosis is history of gastroesophageal variceal hemorrhage and the formation of PVT that may be a risk factor to promote each other. Presently, there are guidelines for diagnosis and treatment of gastroesophageal variceal hemorrhage in liver cirrhosis, but there is still a lack of in-depth understanding of cirrhosis complicated with PVT. This paper summarizes advances in the study of gastroesophageal variceal hemorrhage complicated with PVT in liver cirrhosis in order to enhance the understanding of risk factors for diagnosis and treatment.

[The surgical treatment in adults with idiopathic normal pressure hydrocephalus].

Objective: To investigate the effect of Ventriculoperitoneal shunt (VPS)in adult patients with idiopathic normal pressure hydrocephalus (iNPH). Methods: The patients with idiopathic normal pressure hydrocephalus were reviewed, who were admitted into the Peking union medical college hospital from October 2010 to October 2016.The patients treated via VPS were retrospectively analyzed by collecting the data including clinic features, iNPH score and imaging data. Results: 33 patients were included in the group.3 months after operation, the iNPH scores were significantly decreased (3.0±1.0 vs 6.0±2.5, P<0.01), and there were no difference among 3 month, 6 month and 12 month post operation.The Evans index and the width of the three ventricles were also significantly decreased.1 patient suffered from subdural hematoma and no other complications such as infection, obstruction or death occurred. Conclusions: VPS is an effective treatment approach of iNPH and multidisciplinary team is the key in diagnosis.

Allergic inflammation is exacerbated by allergen-induced type 2 innate lymphoid cells in a murine model of allergic rhinitis.

BACKGROUND: Group 2 innate lymphoid cells (ILC2s) represent a new innate effector leukocyte population that mediates type-2 immune response. However, the contribution of ILC2s to allergic rhinitis (AR) is currently not well defined. OBJECTIVE: To evaluate the potential existence and function of allergen-induced ILC2s in the experimental AR. METHODS: We established a murine model of AR using ovalbumin (OVA) and aluminium hydroxide. The OVA-induced ILC2s were sorted and purified from the mouse nasal-associated lymphoid tissue (NALT). Then, we assessed ILC2s responses to mouse recombinant interleukin (rmIL)-25, anti-IL17RB antibody and CC chemokine ligand (CCL) 25 in the culture. After that, we adoptively transferred the NALT-derived ILC2s alone or plus rmIL-25 or anti-IL17RB antibody to the murine model of AR to investigate their role in the nasal allergic inflammation. RESULTS: We showed that ILC2s could be induced by OVA in the NALT of AR model. They were induced to secrete IL-5 and IL-13 by rmIL-25, and blocking of IL17RB contributed to the decreased production of these cytokines in the culture. We found that CCL25 induced the NALT-derived ILC2s migration through CC chemokine receptor 9 on ILC2s in vitro. Numbers of sneezing and nasal rubbing as well as counts of invasive eosinophils were all enhanced after the adoptive transfer of cultured ILC2s in vitro. The expressions of IL-5, IL-13, IL-25 and CCL25 in the NLF of allergic mice were also increased. CONCLUSION: These findings show that ILC2s play a proinflammatory role in the murine AR model, and also highlight ILC2s as a new target in the future AR therapy.

[Glucose excursion in senior patients with type 2 diabetes mellitus and coronary artery disease].

Objectives: To explore glucose excursion and incidence of hypoglycemia in senior patients with type 2 diabetes mellitus (T2DM) and coronary artery disease (CAD) with different hemoglobin A1c (HbA1c) values. Methods: Eighty-nine outpatients [58 male, 31 female, aged 69.0 (66.0, 73.0) years] diagnosed with T2DM and CAD in Beijing Anzhen Hospital between June 2013 and March 2016 were divided into group A (HbA1c<6.5%, n=25) and group B (HbA1c≥6.5%, n=64). Every patient wore continuous glucose monitoring system (CGMS) for 72 h. Glucose excursion parameters and incidence of hypoglycemia from CGMS readings were calculated. Results: Compared with group B, patients in group A experienced shorter diabetes duration [8.0 (3.5, 15.0) vs 15.0 (8.0, 20.0) years, Z=-2.222, P=0.026], lower standard deviation (SD) of blood glucose from CGMS, mean amplitude of glycemic excursions(MAGE) and mean of the daily differences(MODD) (P=0.001, 0.003, 0.001). However, incidence of hypoglycemia was significantly increased [56.0% (14/25) vs 32.8% (21/64), χ(2)=4.051, P=0.044] in group A. Compared to those who had not experienced hypoglycemia, patients with hypoglycemia had higher SD [1.8(1.4, 2.4) mmol/L vs 1.4(1.1, 1.8) mmol/L, Z=-3.198, P=0.001] and MAGE [6.0(3.2, 7.4) mmol/L vs 3.9(2.7, 4.8 )mmol/L, Z=-2.768, P=0.006] which were appropriate tools for assessing intraday glycemic variability. No statistical difference were found in MODD which was the index for estimating interday glycemic variability. Conclusions: Intensive glycemic control in senior patients with T2DM and CAD had higher incidence of hypoglycemia. Those with hypoglycemia experienced greater intraday glucose excursion.

[The diagnosis and treatment of systemic lupus erythematosus complicated with hydrocephalus].

Objective: To investigate the pathogenesis and management of the hydrocephalus in patients with systemic lupus erythematosus (SLE). Methods: Eight cases of hospitalized lupus patients with hydrocephalus in Peking Union Medical College Hospital from Jan 1990 to Mar 2017 were analyzed retrospectively.We collected the patients' medical records including medical history, CT and/or MRI images and analysis of cerebrospinal fluid via lumbar puncture in order to investigate the pathogenesis of the hydrocephalus in patients with SLE and summarize treatment experience. Results: All the 8 patients with SLE complicated with hydrocephalus were treated with steroids or immunosuppressive agents, and 5 cases were diagnosed with the central nervous system infection. Three cases received ventriculoperitoneal shunt, 5 cases received treatment of medicine.They all were followed up for 2-12 months, of which 3 cases were markedly effective, 1 case effective and 4 cases dead. Conclusion: The pathogenesis of lupus combined with hydrocephalus may have a certain relationship with the central infection, should take effective anti-infection treatment.We recommend cerebrospinal fluid shunt surgery intervention.

[Perioperative management and surgical treatment of neurosurgical critical patients with thrombocytopenia].

OBJECTIVE: To study the perioperative management and surgical treatment of patients with neurosurgical critical diseases and thrombocytopenia. METHODS: Eleven patients with the diagnosis of neurosurgical critical diseases and thrombocytopenia who received surgical treatment in Department of Neurosurgery, Peking Union Medical College Hospital from 2010 to 2015 were reviewed retrospectively. All eleven patients received platelet transfusions preoperatively. The safety and efficacy of surgical treatment were analyzed by GOS score at 6 months after operations. RESULTS: Platelet counts of six patients who received minimally invasive surgery reached 80×10(9) /L by platelet transfusions preoperatively. Platelet counts of five patients who received Craniotomy and ventriculoperitoneal shunt reached 100×10(9) /L by platelet transfusions preoperatively. Eight patients received platelet transfusions postoperatively according to a low platelet count 24 hours after operations. Two patients died after surgery and one died after discharge. All other eight survival patients got well recovery with an average GOS score of 4.5 at six months after operations. CONCLUSIONS: Patients with neurosurgical critical diseases and thrombocytopenia could receive surgical treatment in collaboration with relative departments.

[Use early morning serum cortisollevel to evaluate the effect of Cushing's disease after transsphenoidal surgery].

OBJECTIVE: To predict the therapeutic effect of Cushing's disease after transsphenoidal surgery by using morning serum cortisol level. METHODS: The clinical data of 275 cases that had transsphenoidal surgery in Peking Union Medical College Hospital from 2010 to 2014 were analyzed retrospectively.Early morning serum cortisol level less than 140 nmol/L 3 days postoperation was usedto predict endocrinological remission. And long-term efficacy was evaluated by follow-up. RESULTS: Of the 275 patients, there were 49 males and 226 females; average age was 36.5 years old.Remission wasconfirmed in 201 cases, the remission rate was 73.1%, and 8 cases recurrent duringfollow-up.There were 17 macroadenomas, theremission rate was 47.1%; 258 microadenomas and MRI negative adenomas, the remission rate was 74.8%.And 43 recurrent cases had reoperations; the remission rate was 46.5%. CONCLUSION: Early morningserum cortisol 3 days post operation can evaluate the effectof transsphenoidal surgery, but even if the level of cortisol is less than 140 nmol/L, there is still tumor recurrence.Patients should be follow-up for a lifetime.

A TRPA1 channel that senses thermal stimulus and irritating chemicals in Helicoverpa armigera.

Sensing and responding to changes in the external environment is important for insect survival. Transient receptor potential (TRP) channels are crucial for various sensory modalities including olfaction, vision, hearing, thermosensation and mechanosensation. Here, we identified and characterized a transient receptor potential gene named as HarmTRPA1 in Helicoverpa armigera antennae. HarmTRPA1 was abundantly expressed in the antennae and labial palps. Transcripts of HarmTRPA1 could also be detected in the head and proboscis. Furthermore, functional analyses of HarmTRPA1 were conducted in the Xenopus Oocyte system. The results showed that the HarmTRPA1 channel could be activated by increasing the temperature from 20 to 45 °C. No significant adaptation was observed when the stimulus was repeated. In addition to thermal stimuli, pungent natural compounds including allyl isothiocyanate, cinnamaldehyde and citronellal also activated HarmTRPA1. Taken together, we infer that HarmTRPA1 may function as both a thermal sensor involved in peripheral temperature detection and as a chemical sensor detecting irritating chemicals in vivo. Our data provide valuable insight into the TRPA1 channel in this moth and lay the foundation for developing novel strategies for pest control.

SERS and DFT study of p-hydroxybenzoic acid adsorbed on colloidal silver particles.

In this study, normal Raman spectra of p—hydroxybenzoic acid (PHBA) powder and its surface—enhanced Raman scattering (SERS) spectra in silver colloidal solutions were measured under near infrared excitation conditions. In theoretical calculation, two models of PHBA adsorbed on the surfaces of silver nanoparticles were established. The Raman frequencies of these two models using density functional theory (DFT) method were calculated, and compared with the experimental results. It was found that the calculated Raman frequencies were in good agreement with experimental values, which indicates that there are two enhanced mechanism physical (electromagnetic, EM) enhancement and chemical (charge—transfer, CT) enhancement, in silver colloidal solutions regarding SERS effect. Furthermore, from high—quality SERS spectrum of PHBA obtained in silver colloids, we inferred that PHBA molecules in silver colloids adsorb onto the metal surfaces through carboxyl at a perpendicular orientation. The combination of SERS spectra and DFT calculation is thus useful for studies of the adsorption—orientation of a molecule on a metal colloid.

[Factors associated with readmission within three months of surgery for gastric cancer and their long-term effects on patients' nutritional status and quality of life].

Objective: To analyze the factors associated with readmission within three months of surgery for gastric cancer and the impact of readmission on patients' long-term nutritional status and quality of life. Methods: This was a prospective cohort study comprising patients who underwent radical gastrectomy in the Department of Pancreatic and Gastric Surgery, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences from October 2018 to August 2019. Patients who failed to complete postoperative follow-up, whose body mass index (BMI) could not be accurately estimated, or who were unable to complete a quality-of-life questionnaire were excluded. The patients were followed up for 12 months. Time to, cause(s) of, and outcomes of readmission were followed up 1, 2 and 3 months postoperatively. BMI was followed up 1, 3, 6 and 12 months postoperatively. Results of blood tests were collected and patients' nutritional status and quality of life were assessed 12 months postoperatively. Nutritional status was evaluated by BMI, hemoglobin, albumin, and total lymphocyte count. Quality of life was evaluated using the European Organization for Research in the Treatment of Cancer (EORTC) Quality of Life scale. The higher the scores for global health and functional domains, the better the quality of life, whereas the higher the score in the symptom domain, the worse the quality of life. Results: The study cohort comprised 259 patients with gastric cancer, all of whom were followed up for 3 months and 236 of whom were followed up for 12 months. Forty-four (17.0%) patients were readmitted within 3 months. The commonest reasons for readmission were gastrointestinal dysfunction (16 cases, 36.3%), intestinal obstruction (8 cases, 18.2%), and anastomotic stenosis (8 cases, 18.2%). Logistic regression analysis showed that preoperative Patient-Generated Subjective Global Assessment score ≥ 4 points (OR=1.481, 95% CI: 1.028‒2.132), postoperative complications (OR=3.298, 95%CI:1.416‒7.684) and resection range (OR=1.582, 95% CI:1.057‒2.369) were risk factors for readmission within 3 months of surgery. Compared with patients who had not been readmitted 12 months after surgery, patients who were readmitted within 3 months of surgery tended to have greater decreases in their BMI [-2.36 (-5.13,-0.42) kg/m2 vs. -1.73 (-3.33,-0.33) kg/m2, Z=1.850, P=0.065), significantly lower hemoglobin and albumin concentrations [(122.1±16.6) g/L vs. (129.8±18.4) g/L, t=2.400, P=0.017]; [(40.9±5.0) g/L vs. (43.4±3.3) g/L, t=3.950, P<0.001], and significantly decreased global health scores in the quality of life assessment [83 (67, 100) vs. 100 (83, 100), Z=2.890,P=0.004]. Conclusion: Preoperative nutritional risk, total or proximal radical gastrectomy, and complications during hospitalization are risk factors for readmission within 3 months of surgery for gastric cancer. Perioperative management and postoperative follow-up should be more rigorous. Readmission within 3 months after surgery may be associated with a decline in long-term nutritional status and quality of life. Achieving improvement in long-term nutritional status and quality of life requires tracking of nutritional status, timely evaluation, and appropriate interventions in patients who need readmission.

Shock induced reaction of Ni/Al nanopowder mixture.

Nanopowder Ni/Al mixture (mixed in Al:Ni = 2:1 stoichiometry) was shock compressed by employing single and two-stage light gas gun. The particle size of Al and Ni are 100-200 nm and 50-70 nm respectively, morphologies of Al and Ni are sphere like either. Recovered product was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. According to the XRD spectrum, the mixed powder undergo complete reaction under shock compression, reaction product consist of Ni2Al3, NiAl and corundum structure Al2O3 compound. Grain size of Ni-Al compound is less than 100 nm. With the shock pressure increasing, the ratio of Ni2Al3 decreased obviously. The corundum crystal size is 400-500 nm according to the SEM observation. The results of shock recovery experiments and analysis show that the threshold pressure for reaction of nano size powder Ni/Al mixture is much less than that of micro size powder.